[PATCH v12 0/7] PCI: endpoint: pci-ep-msi: Add embedded doorbell fallback

[PATCH v12 0/7] PCI: endpoint: pci-ep-msi: Add embedded doorbell fallback

[Koichiro Den]

Hi,

Some endpoint platforms cannot use a GIC ITS-backed MSI domain for
EP-side doorbells. In those cases, endpoint function (EPF) drivers
cannot provide a doorbell to the root complex (RC), and features such as
vNTB may fall back to polling with significantly higher latency.

This series adds an alternate doorbell backend based on the PCIe
endpoint controller (EPC)'s integrated eDMA interrupt-emulation feature.
The RC rings the doorbell by doing a single 32-bit MMIO write to an eDMA
doorbell location exposed in a BAR window. The EP side receives a Linux
IRQ that EPF drivers can use as a doorbell interrupt, without relying on
MSI message writes reaching the ITS.

The DesignWare eDMA interrupt-emulation doorbell is wired up as one user
of the generic EPC aux-resource API. Other vendors can support their
MMIO-based doorbells by implementing the EPC aux-resource callbacks:
pci_epc_ops.count_aux_resources() / pci_epc_ops.get_aux_resources().


Dependencies
============

(1). [PATCH 0/2] dmaengine: dw-edma: Interrupt-emulation doorbell support
     https://lore.kernel.org/dmaengine/20260215152216.3393561-1-den@valinux.co.jp/
     Note: already landed in dmaengine/next.


Tested on
=========

v12 re-tested on:

  (1). R-Car S4 Spider: EP <-> RC
  (2). RK3588 Rock 5B (EP) <-> CIX CD8180 Orion O6 (RC)

The EP in both scenarios prints the following in dmesg when running
DOORBELL_TEST:

  pci_epf_test pci_epf_test.0: Can't find MSI domain for EPC
  pci_epf_test pci_epf_test.0: Using embedded (DMA) doorbell fallback

With this series applied, the DOORBELL_TEST succeeds:

  $ ./pci_endpoint_test -t DOORBELL_TEST
  TAP version 13
  1..1
  # Starting 1 tests from 1 test cases.
  #  RUN           pcie_ep_doorbell.DOORBELL_TEST ...
  #            OK  pcie_ep_doorbell.DOORBELL_TEST
  ok 1 pcie_ep_doorbell.DOORBELL_TEST
  # PASSED: 1 / 1 tests passed.
  # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0

IOMMU coverage tested:

  On R-Car S4 Spider EP, DOORBELL_TEST passes with the EP IOMMU both
  enabled and disabled.
  On Rock 5B EP, DOORBELL_TEST passes with the EP IOMMU disabled. The
  enabled case is not applicable, as the EP IOMMU is explicitly disabled
  upstream on this platform.


Performance test: vNTB ping latency
===================================

(*) Re-tested with v12 only to confirm that no regression was introduced
    in v11->v12. No performance difference is expected.

Prerequisite:
  To test on 2x R-Car S4 Spider boards, the following two commits are
  needed:
  - 13f55a7ca773 ("PCI: dwc: rcar-gen4: Change EPC BAR alignment to 4K as
                   per the documentation")
  - f761e0deb4d9 ("PCI: dwc: rcar-gen4: Mark BAR0 and BAR2 as Resizable
                   BARs in endpoint mode")
  Note: these already landed in pci/controller/dwc-rcar-gen4-ep.

Setup:
  - configfs (R-Car S4 Spider in EP mode):

      cd /sys/kernel/config/pci_ep/
      mkdir functions/pci_epf_vntb/func1
      echo 0x1912 >   functions/pci_epf_vntb/func1/vendorid
      echo 0x0030 >   functions/pci_epf_vntb/func1/deviceid
      echo 32 >       functions/pci_epf_vntb/func1/msi_interrupts
      echo 4 >        functions/pci_epf_vntb/func1/pci_epf_vntb.0/db_count
      echo 128 >      functions/pci_epf_vntb/func1/pci_epf_vntb.0/spad_count
      echo 1 >        functions/pci_epf_vntb/func1/pci_epf_vntb.0/num_mws
      echo 0x100000 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw1
      echo 0x1912 >   functions/pci_epf_vntb/func1/pci_epf_vntb.0/vntb_vid
      echo 0x0030 >   functions/pci_epf_vntb/func1/pci_epf_vntb.0/vntb_pid
      echo 0x10 >     functions/pci_epf_vntb/func1/pci_epf_vntb.0/vbus_number
      echo 0 >        functions/pci_epf_vntb/func1/pci_epf_vntb.0/ctrl_bar
      echo 4 >        functions/pci_epf_vntb/func1/pci_epf_vntb.0/db_bar
      echo 2 >        functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw1_bar
      ln -s controllers/e65d0000.pcie-ep functions/pci_epf_vntb/func1/primary/
      echo 1 > controllers/e65d0000.pcie-ep/start

  - ensure ntb_transport/ntb_netdev are loaded on both sides

Results:

  - Without this series (pci/endpoint)

    $ ping -c 10 10.0.0.11
    PING 10.0.0.11 (10.0.0.11) 56(84) bytes of data.
    64 bytes from 10.0.0.11: icmp_seq=1 ttl=64 time=12.1 ms
    64 bytes from 10.0.0.11: icmp_seq=2 ttl=64 time=6.17 ms
    64 bytes from 10.0.0.11: icmp_seq=3 ttl=64 time=12.2 ms
    64 bytes from 10.0.0.11: icmp_seq=4 ttl=64 time=6.10 ms
    64 bytes from 10.0.0.11: icmp_seq=5 ttl=64 time=12.1 ms
    64 bytes from 10.0.0.11: icmp_seq=6 ttl=64 time=9.96 ms
    64 bytes from 10.0.0.11: icmp_seq=7 ttl=64 time=4.04 ms
    64 bytes from 10.0.0.11: icmp_seq=8 ttl=64 time=10.2 ms
    64 bytes from 10.0.0.11: icmp_seq=9 ttl=64 time=4.13 ms
    64 bytes from 10.0.0.11: icmp_seq=10 ttl=64 time=10.0 ms

  - With this series (on top of pci/endpoint + Dependency (1))

    $ ping -c 10 10.0.0.11
    PING 10.0.0.11 (10.0.0.11) 56(84) bytes of data.
    64 bytes from 10.0.0.11: icmp_seq=1 ttl=64 time=0.809 ms
    64 bytes from 10.0.0.11: icmp_seq=2 ttl=64 time=0.756 ms
    64 bytes from 10.0.0.11: icmp_seq=3 ttl=64 time=0.813 ms
    64 bytes from 10.0.0.11: icmp_seq=4 ttl=64 time=0.974 ms
    64 bytes from 10.0.0.11: icmp_seq=5 ttl=64 time=0.874 ms
    64 bytes from 10.0.0.11: icmp_seq=6 ttl=64 time=0.888 ms
    64 bytes from 10.0.0.11: icmp_seq=7 ttl=64 time=0.878 ms
    64 bytes from 10.0.0.11: icmp_seq=8 ttl=64 time=1.11 ms
    64 bytes from 10.0.0.11: icmp_seq=9 ttl=64 time=0.811 ms
    64 bytes from 10.0.0.11: icmp_seq=10 ttl=64 time=0.922 ms


---

Changelog
---------

* v11->v12 changes:
  - Rebased onto the current pci/endpoint:
    185596ad93f5 ("PCI: endpoint: pci-epf-vntb: Implement .get_dma_dev()")
  - Split the EPC auxiliary-resource API into
    pci_epc_count_aux_resources() and pci_epc_get_aux_resources(), both
    returning 0 on success.
  - Added the corresponding count/get callbacks in pci_epc_ops and in the
    DesignWare EPC provider.
  - Updated the embedded doorbell fallback to use the new count/get
    helpers.
  - Stopped warning on duplicate DOORBELL_MMIO resources for now; use the
    first matching resource and add a TODO for future multi-resource
    support.

* v10->v11 changes:
  - Rebased onto the current pci/endpoint:
    e022f0c72c7f ("selftests: pci_endpoint: Skip reserved BARs")
  - Dropped PCI_EPC_AUX_DMA_CTRL_MMIO and PCI_EPC_AUX_DMA_CHAN_DESC from
    this series; they will be added later together with their first real
    consumer.
  - Picked up tags from Frank and Niklas for patches 5/6/7.
  - Dropped tags for patches 1 and 3 due to code changes.
  - Revised the commit message of Patch 2 to better explain the purpose.

* v9->v10 changes:
  - Patch 7/7: report the dma_map_resource() DMA address instead of the
    raw physical address, so EPF drivers do not need to perform any
    additional IOMMU mapping and the semantics match the MSI doorbell
    case.
  - Rebased onto the latest pci/endpoint, and updated dependency references.
  - Re-ran functional tests and vNTB ping-latency measurements, and added
    Rock 5B (EP) <-> Orion O6 (RC) to the test matrix.

* v8->v9 changes:
  - Add a new dependency series (3), which moved the BAR reserved-subregion
    framework + the RK3588 BAR4 example out of v8 (dropping the corresponding
    patches from this series).
  - pci-epf-vntb: rename the duplicate-IRQ helper and invert the return value,
    per Frank's review.
  - pci-epf-test: drop the extra size_add() doorbell-offset check, per Niklas'
    review.
  - pci-ep-msi: add a DWORD alignment check for DOORBELL_MMIO, per Niklas's
    review.
  - Carry over Reviewed-by tags for unchanged patches + drop Reviewed-by tags
    where code changed.
  - Rename the last patch subject (drop 'eDMA' word).

* v7->v8 changes:
  - Deduplicate request_irq()/free_irq() calls based on virq (shared
    IRQ) rather than doorbell type, as suggested during review of v7
    Patch #7.
  - Clean up the pci_epf_alloc_doorbell() error path, as suggested
    during review of v7 Patch #9.
  - Use range_end_overflows_t() instead of an open-coded overflow check,
    following discussion during review of v7 Patch #5.
  - Add a write-data field to the DOORBELL_MMIO aux-resource metadata
    and plumb it through to the embedded doorbell backend (DesignWare
    uses data=0).

* v6->v7 changes:
  - Split out preparatory patches to keep the series below 10 patches.
  - Add support for platforms where the eDMA register block is fixed
    within a reserved BAR window (e.g. RK3588 BAR4) and must be reused
    as-is.
  - Introduce a dedicated virtual IRQ and irq_chip (using
    handle_level_irq) for interrupt-emulation doorbells instead of
    reusing per-channel IRQs. This avoids delivery via different IRQs on
    platforms with chip->nr_irqs > 1.

* v5->v6 changes:
  - Fix a double-free in v5 Patch 8/8 caused by mixing __free(kfree) with
    an explicit kfree(). This is a functional bug (detectable by KASAN),
    hence the respin solely for this fix. Sorry for the noise. No other
    changes.

* v4->v5 changes:
  - Change the series subject now that the series has evolved into a
    consumer-driven set focused on the embedded doorbell fallback and its
    in-tree users (epf-test and epf-vntb).
  - Drop [PATCH v4 01/09] (dw-edma per-channel interrupt routing control)
    from this series for now, so the series focuses on what's needed by the
    current consumer (i.e. the doorbell fallback implementation).
  - Replace the v4 embedded-doorbell "test variant + host/kselftest
    plumbing" with a generic embedded-doorbell fallback in
    pci_epf_alloc_doorbell(), including exposing required IRQ request flags
    to EPF drivers.
  - Two preparatory fix patches (Patch 6/8 and 7/8) to clean up error
    handling and state management ahead of Patch 8/8.
  - Rename *_get_remote_resource() to *_get_aux_resources() and adjust
    relevant variable namings and kernel docs. Discussion may continue.
  - Rework dw-edma per-channel metadata exposure to cache the needed info
    in dw_edma_chip (IRQ number + emulation doorbell offset) and consume it
    from the DesignWare EPC auxiliary resource provider without calling back
    to dw-edma.

* v3->v4 changes:
  - Drop dma_slave_caps.hw_id and the dmaengine selfirq callback
    registration API. Instead, add a dw-edma specific dw_edma_chan_info()
    helper and extend the EPC remote resource metadata accordingly.
  - Add explicit acking for eDMA interrupt emulation and adjust the
    dw-edma IRQ path for embedded-doorbell usage.
  - Replace the previous EPC API smoke test with an embedded doorbell
    test variant (pci-epf-test + pci_endpoint_test/selftests).
  - Rebase onto pci.git controller/dwc commit 43d324eeb08c.

* v2->v3 changes:
  - Replace DWC-specific helpers with a generic EPC remote resource query API.
  - Add pci-epf-test smoke test and host/kselftest support for the new API.
  - Drop the dw-edma-specific notify-only channel and polling approach
    ([PATCH v2 4/7] and [PATCH v2 5/7]), and rework notification handling
    around a generic dmaengine_(un)register_selfirq() API implemented
    by dw-edma.

* v1->v2 changes:
  - Combine the two previously posted series into a single set (per Frank's
    suggestion). Order dmaengine/dw-edma patches first so hw_id support
    lands before the PCI LL-region helper, which assumes
    dma_slave_caps.hw_id availability.

v11: https://lore.kernel.org/linux-pci/20260324083728.3744734-1-den@valinux.co.jp/
v10: https://lore.kernel.org/linux-pci/20260302071427.534158-1-den@valinux.co.jp/
v9: https://lore.kernel.org/linux-pci/20260219081318.4156901-1-den@valinux.co.jp/
v8: https://lore.kernel.org/linux-pci/20260217080601.3808847-1-den@valinux.co.jp/
v7: https://lore.kernel.org/linux-pci/20260215163847.3522572-1-den@valinux.co.jp/
v6: https://lore.kernel.org/all/20260209125316.2132589-1-den@valinux.co.jp/
v5: https://lore.kernel.org/all/20260209062952.2049053-1-den@valinux.co.jp/
v4: https://lore.kernel.org/all/20260206172646.1556847-1-den@valinux.co.jp/
v3: https://lore.kernel.org/all/20260204145440.950609-1-den@valinux.co.jp/
v2: https://lore.kernel.org/all/20260127033420.3460579-1-den@valinux.co.jp/
v1: https://lore.kernel.org/dmaengine/20260126073652.3293564-1-den@valinux.co.jp/
    +
    https://lore.kernel.org/linux-pci/20260126071550.3233631-1-den@valinux.co.jp/


Thanks for reviewing.


Koichiro Den (7):
  PCI: endpoint: Add auxiliary resource query API
  PCI: dwc: Record integrated eDMA register window
  PCI: dwc: ep: Expose integrated eDMA resources via EPC aux-resource
    API
  PCI: endpoint: pci-ep-msi: Refactor doorbell allocation for new
    backends
  PCI: endpoint: pci-epf-vntb: Reuse pre-exposed doorbells and IRQ flags
  PCI: endpoint: pci-epf-test: Reuse pre-exposed doorbell targets
  PCI: endpoint: pci-ep-msi: Add embedded doorbell fallback

 .../pci/controller/dwc/pcie-designware-ep.c   | 123 ++++++++++++
 drivers/pci/controller/dwc/pcie-designware.c  |   4 +
 drivers/pci/controller/dwc/pcie-designware.h  |   2 +
 drivers/pci/endpoint/functions/pci-epf-test.c |  84 +++++---
 drivers/pci/endpoint/functions/pci-epf-vntb.c |  61 +++++-
 drivers/pci/endpoint/pci-ep-msi.c             | 183 ++++++++++++++++--
 drivers/pci/endpoint/pci-epc-core.c           |  83 ++++++++
 include/linux/pci-epc.h                       |  53 +++++
 include/linux/pci-epf.h                       |  31 ++-
 9 files changed, 577 insertions(+), 47 deletions(-)

-- 
2.51.0

[PATCH v12 1/7] PCI: endpoint: Add auxiliary resource query API

[Koichiro Den]

Endpoint controller drivers may integrate auxiliary blocks (e.g. DMA
engines) whose register windows and descriptor memories metadata need to
be exposed to a remote peer. Endpoint function drivers need a generic
way to discover such resources without hard-coding controller-specific
helpers.

Add pci_epc_count_aux_resources() / pci_epc_get_aux_resources() and the
corresponding pci_epc_ops callbacks. The count helper returns the number
of available resources via an output parameter, while the get helper
fills a caller-provided array of resources described by type, physical
address and size, plus type-specific metadata.

Suggested-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
Changes in v12:
  - Add pci_epc_count_aux_resources() and pci_epc_ops.count_aux_resources
  - Use pci_epc_function_is_valid() instead of open-coding

 drivers/pci/endpoint/pci-epc-core.c | 83 +++++++++++++++++++++++++++++
 include/linux/pci-epc.h             | 53 ++++++++++++++++++
 2 files changed, 136 insertions(+)

diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
index 6c3c58185fc5..fded71a19d71 100644
--- a/drivers/pci/endpoint/pci-epc-core.c
+++ b/drivers/pci/endpoint/pci-epc-core.c
@@ -156,6 +156,89 @@ const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
 }
 EXPORT_SYMBOL_GPL(pci_epc_get_features);
 
+/**
+ * pci_epc_count_aux_resources() - count EPC-provided auxiliary resources
+ * @epc: EPC device
+ * @func_no: function number
+ * @vfunc_no: virtual function number
+ * @num_resources: returned number of auxiliary resources
+ *
+ * Some EPC backends integrate auxiliary blocks (e.g. DMA engines) whose control
+ * registers and/or descriptor memories can be exposed to the host by mapping
+ * them into BAR space. This helper queries how many such resources the backend
+ * provides.
+ *
+ * Return: 0 on success, -EOPNOTSUPP if the backend does not support auxiliary
+ * resource queries, or another -errno on failure.
+ */
+int pci_epc_count_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+				int *num_resources)
+{
+	int ret;
+
+	if (!num_resources)
+		return -EINVAL;
+
+	if (!epc || !epc->ops)
+		return -EINVAL;
+
+	if (!pci_epc_function_is_valid(epc, func_no, vfunc_no))
+		return -EINVAL;
+
+	if (!epc->ops->count_aux_resources)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&epc->lock);
+	ret = epc->ops->count_aux_resources(epc, func_no, vfunc_no,
+					    num_resources);
+	mutex_unlock(&epc->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pci_epc_count_aux_resources);
+
+/**
+ * pci_epc_get_aux_resources() - query EPC-provided auxiliary resources
+ * @epc: EPC device
+ * @func_no: function number
+ * @vfunc_no: virtual function number
+ * @resources: output array
+ * @num_resources: size of @resources array in entries
+ *
+ * Some EPC backends integrate auxiliary blocks (e.g. DMA engines) whose control
+ * registers and/or descriptor memories can be exposed to the host by mapping
+ * them into BAR space. This helper queries the backend for such resources.
+ *
+ * Return: 0 on success, -EOPNOTSUPP if the backend does not support auxiliary
+ * resource queries, or another -errno on failure.
+ */
+int pci_epc_get_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+			      struct pci_epc_aux_resource *resources,
+			      int num_resources)
+{
+	int ret;
+
+	if (!resources || num_resources <= 0)
+		return -EINVAL;
+
+	if (!epc || !epc->ops)
+		return -EINVAL;
+
+	if (!pci_epc_function_is_valid(epc, func_no, vfunc_no))
+		return -EINVAL;
+
+	if (!epc->ops->get_aux_resources)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&epc->lock);
+	ret = epc->ops->get_aux_resources(epc, func_no, vfunc_no, resources,
+					  num_resources);
+	mutex_unlock(&epc->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pci_epc_get_aux_resources);
+
 /**
  * pci_epc_stop() - stop the PCI link
  * @epc: the link of the EPC device that has to be stopped
diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
index 334c2b7578d0..d8b81fc6ca6a 100644
--- a/include/linux/pci-epc.h
+++ b/include/linux/pci-epc.h
@@ -61,6 +61,47 @@ struct pci_epc_map {
 	void __iomem	*virt_addr;
 };
 
+/**
+ * enum pci_epc_aux_resource_type - auxiliary resource type identifiers
+ * @PCI_EPC_AUX_DOORBELL_MMIO: Doorbell MMIO, that might be outside the DMA
+ *                             controller register window
+ *
+ * EPC backends may expose auxiliary blocks (e.g. DMA engines) by mapping their
+ * register windows and descriptor memories into BAR space. This enum
+ * identifies the type of each exposable resource.
+ */
+enum pci_epc_aux_resource_type {
+	PCI_EPC_AUX_DOORBELL_MMIO,
+};
+
+/**
+ * struct pci_epc_aux_resource - a physical auxiliary resource that may be
+ *                               exposed for peer use
+ * @type:       resource type, see enum pci_epc_aux_resource_type
+ * @phys_addr:  physical base address of the resource
+ * @size:       size of the resource in bytes
+ * @bar:        BAR number where this resource is already exposed to the RC
+ *              (NO_BAR if not)
+ * @bar_offset: offset within @bar where the resource starts (valid iff
+ *              @bar != NO_BAR)
+ * @u:          type-specific metadata
+ */
+struct pci_epc_aux_resource {
+	enum pci_epc_aux_resource_type type;
+	phys_addr_t phys_addr;
+	resource_size_t size;
+	enum pci_barno bar;
+	resource_size_t bar_offset;
+
+	union {
+		/* PCI_EPC_AUX_DOORBELL_MMIO */
+		struct {
+			int irq; /* IRQ number for the doorbell handler */
+			u32 data; /* write value to ring the doorbell */
+		} db_mmio;
+	} u;
+};
+
 /**
  * struct pci_epc_ops - set of function pointers for performing EPC operations
  * @write_header: ops to populate configuration space header
@@ -84,6 +125,8 @@ struct pci_epc_map {
  * @start: ops to start the PCI link
  * @stop: ops to stop the PCI link
  * @get_features: ops to get the features supported by the EPC
+ * @count_aux_resources: ops to count controller-owned auxiliary resources
+ * @get_aux_resources: ops to retrieve controller-owned auxiliary resources
  * @owner: the module owner containing the ops
  */
 struct pci_epc_ops {
@@ -115,6 +158,11 @@ struct pci_epc_ops {
 	void	(*stop)(struct pci_epc *epc);
 	const struct pci_epc_features* (*get_features)(struct pci_epc *epc,
 						       u8 func_no, u8 vfunc_no);
+	int	(*count_aux_resources)(struct pci_epc *epc, u8 func_no,
+				       u8 vfunc_no, int *num_resources);
+	int	(*get_aux_resources)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+				     struct pci_epc_aux_resource *resources,
+				     int num_resources);
 	struct module *owner;
 };
 
@@ -339,6 +387,11 @@ int pci_epc_start(struct pci_epc *epc);
 void pci_epc_stop(struct pci_epc *epc);
 const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
 						    u8 func_no, u8 vfunc_no);
+int pci_epc_count_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+				int *num_resources);
+int pci_epc_get_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+			      struct pci_epc_aux_resource *resources,
+			      int num_resources);
 enum pci_barno
 pci_epc_get_first_free_bar(const struct pci_epc_features *epc_features);
 enum pci_barno pci_epc_get_next_free_bar(const struct pci_epc_features
-- 
2.51.0

[PATCH v12 2/7] PCI: dwc: Record integrated eDMA register window

[Koichiro Den]

Some DesignWare PCIe controllers integrate an eDMA block whose registers
are located in a dedicated register window.

The EP-side aux-resource code exposes an interrupt-emulation doorbell
register (DOORBELL_MMIO) from that window. Its location is derived from
the start of the eDMA register window plus the doorbell offset already
provided by dw-edma, and the window size is used to validate the
computed register location.

Record the physical base and size of the integrated eDMA register window
in struct dw_pcie so the EP-side DesignWare aux-resource provider can
construct that doorbell resource.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Tested-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
 drivers/pci/controller/dwc/pcie-designware.c | 4 ++++
 drivers/pci/controller/dwc/pcie-designware.h | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 5741c09dde7f..f82ed189f6ae 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -162,8 +162,12 @@ int dw_pcie_get_resources(struct dw_pcie *pci)
 			pci->edma.reg_base = devm_ioremap_resource(pci->dev, res);
 			if (IS_ERR(pci->edma.reg_base))
 				return PTR_ERR(pci->edma.reg_base);
+			pci->edma_reg_phys = res->start;
+			pci->edma_reg_size = resource_size(res);
 		} else if (pci->atu_size >= 2 * DEFAULT_DBI_DMA_OFFSET) {
 			pci->edma.reg_base = pci->atu_base + DEFAULT_DBI_DMA_OFFSET;
+			pci->edma_reg_phys = pci->atu_phys_addr + DEFAULT_DBI_DMA_OFFSET;
+			pci->edma_reg_size = pci->atu_size - DEFAULT_DBI_DMA_OFFSET;
 		}
 	}
 
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index ae6389dd9caa..52f26663e8b1 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -541,6 +541,8 @@ struct dw_pcie {
 	int			max_link_speed;
 	u8			n_fts[2];
 	struct dw_edma_chip	edma;
+	phys_addr_t		edma_reg_phys;
+	resource_size_t		edma_reg_size;
 	bool			l1ss_support;	/* L1 PM Substates support */
 	struct clk_bulk_data	app_clks[DW_PCIE_NUM_APP_CLKS];
 	struct clk_bulk_data	core_clks[DW_PCIE_NUM_CORE_CLKS];
-- 
2.51.0

[PATCH v12 3/7] PCI: dwc: ep: Expose integrated eDMA resources via EPC aux-resource API

[Koichiro Den]

Implement the EPC aux-resource API for DesignWare endpoint controllers
with integrated eDMA.

Currently, only report an interrupt-emulation doorbell register
(PCI_EPC_AUX_DOORBELL_MMIO), including its Linux IRQ and the write data
needed to trigger the interrupt.

If the DMA controller MMIO window is already exposed via a
platform-owned fixed BAR subregion, also provide the BAR number and
offset so EPF drivers can reuse it without reprogramming the BAR.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
Changes in v12:
  - Implement the new callback .count_aux_resources().
    dw_pcie_ep_get_aux_resources() is refined.

 .../pci/controller/dwc/pcie-designware-ep.c   | 123 ++++++++++++++++++
 1 file changed, 123 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
index 386bfb7b2bf6..b92bc37404c5 100644
--- a/drivers/pci/controller/dwc/pcie-designware-ep.c
+++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
@@ -9,6 +9,7 @@
 #include <linux/align.h>
 #include <linux/bitfield.h>
 #include <linux/of.h>
+#include <linux/overflow.h>
 #include <linux/platform_device.h>
 
 #include "pcie-designware.h"
@@ -817,6 +818,126 @@ dw_pcie_ep_get_features(struct pci_epc *epc, u8 func_no, u8 vfunc_no)
 	return ep->ops->get_features(ep);
 }
 
+static const struct pci_epc_bar_rsvd_region *
+dw_pcie_ep_find_bar_rsvd_region(struct dw_pcie_ep *ep,
+				enum pci_epc_bar_rsvd_region_type type,
+				enum pci_barno *bar,
+				resource_size_t *bar_offset)
+{
+	const struct pci_epc_features *features;
+	const struct pci_epc_bar_desc *bar_desc;
+	const struct pci_epc_bar_rsvd_region *r;
+	int i, j;
+
+	if (!ep->ops->get_features)
+		return NULL;
+
+	features = ep->ops->get_features(ep);
+	if (!features)
+		return NULL;
+
+	for (i = BAR_0; i <= BAR_5; i++) {
+		bar_desc = &features->bar[i];
+
+		if (!bar_desc->nr_rsvd_regions || !bar_desc->rsvd_regions)
+			continue;
+
+		for (j = 0; j < bar_desc->nr_rsvd_regions; j++) {
+			r = &bar_desc->rsvd_regions[j];
+
+			if (r->type != type)
+				continue;
+
+			if (bar)
+				*bar = i;
+			if (bar_offset)
+				*bar_offset = r->offset;
+			return r;
+		}
+	}
+
+	return NULL;
+}
+
+static int
+dw_pcie_ep_count_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+			       int *num_resources)
+{
+	struct dw_pcie_ep *ep = epc_get_drvdata(epc);
+	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
+	struct dw_edma_chip *edma = &pci->edma;
+
+	*num_resources = 0;
+
+	if (!pci->edma_reg_size)
+		return 0;
+
+	if (edma->db_offset == ~0)
+		return 0;
+
+	*num_resources = 1;
+	return 0;
+}
+
+static int
+dw_pcie_ep_get_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+			     struct pci_epc_aux_resource *resources,
+			     int num_resources)
+{
+	struct dw_pcie_ep *ep = epc_get_drvdata(epc);
+	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
+	const struct pci_epc_bar_rsvd_region *rsvd;
+	struct dw_edma_chip *edma = &pci->edma;
+	enum pci_barno dma_ctrl_bar = NO_BAR;
+	resource_size_t db_offset = edma->db_offset;
+	resource_size_t dma_ctrl_bar_offset = 0;
+	resource_size_t dma_reg_size;
+	int count;
+	int ret;
+
+	ret = dw_pcie_ep_count_aux_resources(epc, func_no, vfunc_no, &count);
+	if (ret)
+		return ret;
+
+	if (num_resources < count)
+		return -ENOSPC;
+
+	if (!count)
+		return 0;
+
+	dma_reg_size = pci->edma_reg_size;
+
+	rsvd = dw_pcie_ep_find_bar_rsvd_region(ep,
+					       PCI_EPC_BAR_RSVD_DMA_CTRL_MMIO,
+					       &dma_ctrl_bar,
+					       &dma_ctrl_bar_offset);
+	if (rsvd && rsvd->size < dma_reg_size)
+		dma_reg_size = rsvd->size;
+
+	/*
+	 * For interrupt-emulation doorbells, report a standalone resource
+	 * instead of bundling it into the DMA controller MMIO resource.
+	 */
+	if (range_end_overflows_t(resource_size_t, db_offset,
+				  sizeof(u32), dma_reg_size))
+		return -EINVAL;
+
+	resources[0] = (struct pci_epc_aux_resource) {
+		.type = PCI_EPC_AUX_DOORBELL_MMIO,
+		.phys_addr = pci->edma_reg_phys + db_offset,
+		.size = sizeof(u32),
+		.bar = dma_ctrl_bar,
+		.bar_offset = dma_ctrl_bar != NO_BAR ?
+				dma_ctrl_bar_offset + db_offset : 0,
+		.u.db_mmio = {
+			.irq = edma->db_irq,
+			.data = 0, /* write 0 to assert */
+		},
+	};
+
+	return 0;
+}
+
 static const struct pci_epc_ops epc_ops = {
 	.write_header		= dw_pcie_ep_write_header,
 	.set_bar		= dw_pcie_ep_set_bar,
@@ -832,6 +953,8 @@ static const struct pci_epc_ops epc_ops = {
 	.start			= dw_pcie_ep_start,
 	.stop			= dw_pcie_ep_stop,
 	.get_features		= dw_pcie_ep_get_features,
+	.count_aux_resources	= dw_pcie_ep_count_aux_resources,
+	.get_aux_resources	= dw_pcie_ep_get_aux_resources,
 };
 
 /**
-- 
2.51.0

[PATCH v12 4/7] PCI: endpoint: pci-ep-msi: Refactor doorbell allocation for new backends

[Koichiro Den]

Prepare pci-ep-msi for non-MSI doorbell backends.

Factor MSI doorbell allocation into a helper and extend struct
pci_epf_doorbell_msg with:

  - irq_flags: required IRQ request flags (e.g. IRQF_SHARED for some
    backends)
  - type: doorbell backend type
  - bar/offset: pre-exposed doorbell target location, if any

Initialize these fields for the existing MSI-backed doorbell
implementation.

Also add PCI_EPF_DOORBELL_EMBEDDED type, which is to be implemented in a
follow-up patch.

No functional changes.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Tested-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
 drivers/pci/endpoint/pci-ep-msi.c | 54 ++++++++++++++++++++++---------
 include/linux/pci-epf.h           | 23 +++++++++++--
 2 files changed, 60 insertions(+), 17 deletions(-)

diff --git a/drivers/pci/endpoint/pci-ep-msi.c b/drivers/pci/endpoint/pci-ep-msi.c
index 1395919571f8..85fe46103220 100644
--- a/drivers/pci/endpoint/pci-ep-msi.c
+++ b/drivers/pci/endpoint/pci-ep-msi.c
@@ -8,6 +8,7 @@
 
 #include <linux/device.h>
 #include <linux/export.h>
+#include <linux/interrupt.h>
 #include <linux/irqdomain.h>
 #include <linux/module.h>
 #include <linux/msi.h>
@@ -35,23 +36,13 @@ static void pci_epf_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
 	pci_epc_put(epc);
 }
 
-int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
+static int pci_epf_alloc_doorbell_msi(struct pci_epf *epf, u16 num_db)
 {
-	struct pci_epc *epc = epf->epc;
+	struct pci_epf_doorbell_msg *msg;
 	struct device *dev = &epf->dev;
+	struct pci_epc *epc = epf->epc;
 	struct irq_domain *domain;
-	void *msg;
-	int ret;
-	int i;
-
-	/* TODO: Multi-EPF support */
-	if (list_first_entry_or_null(&epc->pci_epf, struct pci_epf, list) != epf) {
-		dev_err(dev, "MSI doorbell doesn't support multiple EPF\n");
-		return -EINVAL;
-	}
-
-	if (epf->db_msg)
-		return -EBUSY;
+	int ret, i;
 
 	domain = of_msi_map_get_device_domain(epc->dev.parent, 0,
 					      DOMAIN_BUS_PLATFORM_MSI);
@@ -74,6 +65,12 @@ int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
 	if (!msg)
 		return -ENOMEM;
 
+	for (i = 0; i < num_db; i++)
+		msg[i] = (struct pci_epf_doorbell_msg) {
+			.type = PCI_EPF_DOORBELL_MSI,
+			.bar = NO_BAR,
+		};
+
 	epf->num_db = num_db;
 	epf->db_msg = msg;
 
@@ -90,13 +87,40 @@ int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
 	for (i = 0; i < num_db; i++)
 		epf->db_msg[i].virq = msi_get_virq(epc->dev.parent, i);
 
+	return 0;
+}
+
+int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
+{
+	struct pci_epc *epc = epf->epc;
+	struct device *dev = &epf->dev;
+	int ret;
+
+	/* TODO: Multi-EPF support */
+	if (list_first_entry_or_null(&epc->pci_epf, struct pci_epf, list) != epf) {
+		dev_err(dev, "Doorbell doesn't support multiple EPF\n");
+		return -EINVAL;
+	}
+
+	if (epf->db_msg)
+		return -EBUSY;
+
+	ret = pci_epf_alloc_doorbell_msi(epf, num_db);
+	if (!ret)
+		return 0;
+
+	dev_err(dev, "Failed to allocate doorbell: %d\n", ret);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(pci_epf_alloc_doorbell);
 
 void pci_epf_free_doorbell(struct pci_epf *epf)
 {
-	platform_device_msi_free_irqs_all(epf->epc->dev.parent);
+	if (!epf->db_msg)
+		return;
+
+	if (epf->db_msg[0].type == PCI_EPF_DOORBELL_MSI)
+		platform_device_msi_free_irqs_all(epf->epc->dev.parent);
 
 	kfree(epf->db_msg);
 	epf->db_msg = NULL;
diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
index 7737a7c03260..cd747447a1ea 100644
--- a/include/linux/pci-epf.h
+++ b/include/linux/pci-epf.h
@@ -152,14 +152,33 @@ struct pci_epf_bar {
 	struct pci_epf_bar_submap	*submap;
 };
 
+enum pci_epf_doorbell_type {
+	PCI_EPF_DOORBELL_MSI = 0,
+	PCI_EPF_DOORBELL_EMBEDDED,
+};
+
 /**
  * struct pci_epf_doorbell_msg - represents doorbell message
- * @msg: MSI message
- * @virq: IRQ number of this doorbell MSI message
+ * @msg: Doorbell address/data pair to be mapped into BAR space.
+ *       For MSI-backed doorbells this is the MSI message, while for
+ *       "embedded" doorbells this represents an MMIO write that asserts
+ *       an interrupt on the EP side.
+ * @virq: IRQ number of this doorbell message
+ * @irq_flags: Required flags for request_irq()/request_threaded_irq().
+ *             Callers may OR-in additional flags (e.g. IRQF_ONESHOT).
+ * @type: Doorbell type.
+ * @bar: BAR number where the doorbell target is already exposed to the RC
+ *       (NO_BAR if not)
+ * @offset: offset within @bar for the doorbell target (valid iff
+ *          @bar != NO_BAR)
  */
 struct pci_epf_doorbell_msg {
 	struct msi_msg msg;
 	int virq;
+	unsigned long irq_flags;
+	enum pci_epf_doorbell_type type;
+	enum pci_barno bar;
+	resource_size_t offset;
 };
 
 /**
-- 
2.51.0

[PATCH v12 5/7] PCI: endpoint: pci-epf-vntb: Reuse pre-exposed doorbells and IRQ flags

[Koichiro Den]

Support doorbell backends where the doorbell target is already exposed
via a platform-owned fixed BAR mapping and/or where the doorbell IRQ
must be requested with specific flags.

When pci_epf_alloc_doorbell() provides db_msg[].bar/offset, reuse the
pre-exposed BAR window and skip programming a new inbound mapping. Also
honor db_msg[].irq_flags when requesting the doorbell IRQ.

Multiple doorbells may share the same Linux IRQ. Avoid duplicate
request_irq() calls by requesting each unique virq once.

Make pci-epf-vntb work with platform-defined or embedded doorbell
backends without exposing backend-specific details to the consumer
layer.

Tested-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
 drivers/pci/endpoint/functions/pci-epf-vntb.c | 61 ++++++++++++++++++-
 1 file changed, 58 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
index 2256c3062b1a..b493a300da4d 100644
--- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
+++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
@@ -134,6 +134,11 @@ struct epf_ntb {
 	u16 vntb_vid;
 
 	bool linkup;
+
+	/*
+	 * True when doorbells are interrupt-driven (MSI or embedded), false
+	 * when polled.
+	 */
 	bool msi_doorbell;
 	u32 spad_size;
 
@@ -517,6 +522,17 @@ static int epf_ntb_configure_interrupt(struct epf_ntb *ntb)
 	return 0;
 }
 
+static bool epf_ntb_db_irq_is_duplicated(const struct pci_epf *epf, unsigned int idx)
+{
+	unsigned int i;
+
+	for (i = 0; i < idx; i++)
+		if (epf->db_msg[i].virq == epf->db_msg[idx].virq)
+			return true;
+
+	return false;
+}
+
 static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
 					    struct pci_epf_bar *db_bar,
 					    const struct pci_epc_features *epc_features,
@@ -533,9 +549,24 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
 	if (ret)
 		return ret;
 
+	/*
+	 * The doorbell target may already be exposed by a platform-owned fixed
+	 * BAR. In that case, we must reuse it and the requested db_bar must
+	 * match.
+	 */
+	if (epf->db_msg[0].bar != NO_BAR && epf->db_msg[0].bar != barno) {
+		ret = -EINVAL;
+		goto err_free_doorbell;
+	}
+
 	for (req = 0; req < ntb->db_count; req++) {
+		/* Avoid requesting duplicate handlers */
+		if (epf_ntb_db_irq_is_duplicated(epf, req))
+			continue;
+
 		ret = request_irq(epf->db_msg[req].virq, epf_ntb_doorbell_handler,
-				  0, "pci_epf_vntb_db", ntb);
+				  epf->db_msg[req].irq_flags, "pci_epf_vntb_db",
+				  ntb);
 
 		if (ret) {
 			dev_err(&epf->dev,
@@ -545,6 +576,22 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
 		}
 	}
 
+	if (epf->db_msg[0].bar != NO_BAR) {
+		for (i = 0; i < ntb->db_count; i++) {
+			msg = &epf->db_msg[i].msg;
+
+			if (epf->db_msg[i].bar != barno) {
+				ret = -EINVAL;
+				goto err_free_irq;
+			}
+
+			ntb->reg->db_data[i] = msg->data;
+			ntb->reg->db_offset[i] = epf->db_msg[i].offset;
+		}
+		goto out;
+	}
+
+	/* Program inbound mapping for the doorbell */
 	msg = &epf->db_msg[0].msg;
 
 	high = 0;
@@ -591,6 +638,7 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
 		ntb->reg->db_offset[i] = offset;
 	}
 
+out:
 	ntb->reg->db_entry_size = 0;
 
 	ntb->msi_doorbell = true;
@@ -598,9 +646,13 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
 	return 0;
 
 err_free_irq:
-	for (req--; req >= 0; req--)
+	for (req--; req >= 0; req--) {
+		if (epf_ntb_db_irq_is_duplicated(epf, req))
+			continue;
 		free_irq(epf->db_msg[req].virq, ntb);
+	}
 
+err_free_doorbell:
 	pci_epf_free_doorbell(ntb->epf);
 	return ret;
 }
@@ -666,8 +718,11 @@ static void epf_ntb_db_bar_clear(struct epf_ntb *ntb)
 	if (ntb->msi_doorbell) {
 		int i;
 
-		for (i = 0; i < ntb->db_count; i++)
+		for (i = 0; i < ntb->db_count; i++) {
+			if (epf_ntb_db_irq_is_duplicated(ntb->epf, i))
+				continue;
 			free_irq(ntb->epf->db_msg[i].virq, ntb);
+		}
 	}
 
 	if (ntb->epf->db_msg)
-- 
2.51.0

[PATCH v12 6/7] PCI: endpoint: pci-epf-test: Reuse pre-exposed doorbell targets

[Koichiro Den]

pci-epf-test advertises the doorbell target to the RC as a BAR number
and an offset, and the RC rings the doorbell with a single DWORD MMIO
write.

Some doorbell backends may report that the doorbell target is already
exposed via a platform-owned fixed BAR (db_msg[0].bar/offset). In that
case, reuse the pre-exposed window and do not reprogram the BAR with
pci_epc_set_bar().

Also honor db_msg[0].irq_flags when requesting the doorbell IRQ, and
only restore the original BAR mapping on disable if pci-epf-test
programmed it.

Tested-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
 drivers/pci/endpoint/functions/pci-epf-test.c | 84 +++++++++++++------
 1 file changed, 57 insertions(+), 27 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index 14e61ebe1f11..b6c865b0883d 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -93,6 +93,7 @@ struct pci_epf_test {
 	bool			dma_private;
 	const struct pci_epc_features *epc_features;
 	struct pci_epf_bar	db_bar;
+	bool			db_bar_programmed;
 	size_t			bar_size[PCI_STD_NUM_BARS];
 };
 
@@ -732,7 +733,9 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
 {
 	u32 status = le32_to_cpu(reg->status);
 	struct pci_epf *epf = epf_test->epf;
+	struct pci_epf_doorbell_msg *db;
 	struct pci_epc *epc = epf->epc;
+	unsigned long irq_flags;
 	struct msi_msg *msg;
 	enum pci_barno bar;
 	size_t offset;
@@ -742,13 +745,28 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
 	if (ret)
 		goto set_status_err;
 
-	msg = &epf->db_msg[0].msg;
-	bar = pci_epc_get_next_free_bar(epf_test->epc_features, epf_test->test_reg_bar + 1);
-	if (bar < BAR_0)
-		goto err_doorbell_cleanup;
+	db = &epf->db_msg[0];
+	msg = &db->msg;
+	epf_test->db_bar_programmed = false;
+
+	if (db->bar != NO_BAR) {
+		/*
+		 * The doorbell target is already exposed via a platform-owned
+		 * fixed BAR
+		 */
+		bar = db->bar;
+		offset = db->offset;
+	} else {
+		bar = pci_epc_get_next_free_bar(epf_test->epc_features,
+						epf_test->test_reg_bar + 1);
+		if (bar < BAR_0)
+			goto err_doorbell_cleanup;
+	}
+
+	irq_flags = epf->db_msg[0].irq_flags | IRQF_ONESHOT;
 
 	ret = request_threaded_irq(epf->db_msg[0].virq, NULL,
-				   pci_epf_test_doorbell_handler, IRQF_ONESHOT,
+				   pci_epf_test_doorbell_handler, irq_flags,
 				   "pci-ep-test-doorbell", epf_test);
 	if (ret) {
 		dev_err(&epf->dev,
@@ -760,22 +778,30 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
 	reg->doorbell_data = cpu_to_le32(msg->data);
 	reg->doorbell_bar = cpu_to_le32(bar);
 
-	msg = &epf->db_msg[0].msg;
-	ret = pci_epf_align_inbound_addr(epf, bar, ((u64)msg->address_hi << 32) | msg->address_lo,
-					 &epf_test->db_bar.phys_addr, &offset);
+	if (db->bar == NO_BAR) {
+		ret = pci_epf_align_inbound_addr(epf, bar,
+						 ((u64)msg->address_hi << 32) |
+						 msg->address_lo,
+						 &epf_test->db_bar.phys_addr,
+						 &offset);
 
-	if (ret)
-		goto err_free_irq;
+		if (ret)
+			goto err_free_irq;
+	}
 
 	reg->doorbell_offset = cpu_to_le32(offset);
 
-	epf_test->db_bar.barno = bar;
-	epf_test->db_bar.size = epf->bar[bar].size;
-	epf_test->db_bar.flags = epf->bar[bar].flags;
+	if (db->bar == NO_BAR) {
+		epf_test->db_bar.barno = bar;
+		epf_test->db_bar.size = epf->bar[bar].size;
+		epf_test->db_bar.flags = epf->bar[bar].flags;
 
-	ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &epf_test->db_bar);
-	if (ret)
-		goto err_free_irq;
+		ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &epf_test->db_bar);
+		if (ret)
+			goto err_free_irq;
+
+		epf_test->db_bar_programmed = true;
+	}
 
 	status |= STATUS_DOORBELL_ENABLE_SUCCESS;
 	reg->status = cpu_to_le32(status);
@@ -805,17 +831,21 @@ static void pci_epf_test_disable_doorbell(struct pci_epf_test *epf_test,
 	free_irq(epf->db_msg[0].virq, epf_test);
 	pci_epf_test_doorbell_cleanup(epf_test);
 
-	/*
-	 * The doorbell feature temporarily overrides the inbound translation
-	 * to point to the address stored in epf_test->db_bar.phys_addr, i.e.,
-	 * it calls set_bar() twice without ever calling clear_bar(), as
-	 * calling clear_bar() would clear the BAR's PCI address assigned by
-	 * the host. Thus, when disabling the doorbell, restore the inbound
-	 * translation to point to the memory allocated for the BAR.
-	 */
-	ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &epf->bar[bar]);
-	if (ret)
-		goto set_status_err;
+	if (epf_test->db_bar_programmed) {
+		/*
+		 * The doorbell feature temporarily overrides the inbound translation
+		 * to point to the address stored in epf_test->db_bar.phys_addr, i.e.,
+		 * it calls set_bar() twice without ever calling clear_bar(), as
+		 * calling clear_bar() would clear the BAR's PCI address assigned by
+		 * the host. Thus, when disabling the doorbell, restore the inbound
+		 * translation to point to the memory allocated for the BAR.
+		 */
+		ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &epf->bar[bar]);
+		if (ret)
+			goto set_status_err;
+
+		epf_test->db_bar_programmed = false;
+	}
 
 	status |= STATUS_DOORBELL_DISABLE_SUCCESS;
 	reg->status = cpu_to_le32(status);
-- 
2.51.0

[PATCH v12 7/7] PCI: endpoint: pci-ep-msi: Add embedded doorbell fallback

[Koichiro Den]

Some endpoint platforms cannot use platform MSI / GIC ITS to implement
EP-side doorbells. In those cases, EPF drivers cannot provide an
interrupt-driven doorbell and often fall back to polling.

Add an "embedded" doorbell backend that uses a controller-integrated
doorbell target (e.g. DesignWare integrated eDMA interrupt-emulation
doorbell).

The backend locates the doorbell register and a corresponding Linux IRQ
via the EPC aux-resource API. If the doorbell register is already
exposed via a fixed BAR mapping, provide BAR+offset. Otherwise provide
the DMA address returned by dma_map_resource() (which may be an IOVA
when an IOMMU is enabled) so EPF drivers can map it into BAR space.

When MSI doorbell allocation fails with -ENODEV,
pci_epf_alloc_doorbell() falls back to this embedded backend.

Suggested-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
Changes in v12:
  - Use the new pci_epc_count_aux_resources()
  - Add TODO comment and defer multiple DOORBELL_MMIO resources per EPC
    case.

 drivers/pci/endpoint/pci-ep-msi.c | 135 +++++++++++++++++++++++++++++-
 include/linux/pci-epf.h           |   8 ++
 2 files changed, 140 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/endpoint/pci-ep-msi.c b/drivers/pci/endpoint/pci-ep-msi.c
index 85fe46103220..0d720556205b 100644
--- a/drivers/pci/endpoint/pci-ep-msi.c
+++ b/drivers/pci/endpoint/pci-ep-msi.c
@@ -6,6 +6,8 @@
  * Author: Frank Li <Frank.Li@nxp.com>
  */
 
+#include <linux/align.h>
+#include <linux/cleanup.h>
 #include <linux/device.h>
 #include <linux/export.h>
 #include <linux/interrupt.h>
@@ -36,6 +38,113 @@ static void pci_epf_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
 	pci_epc_put(epc);
 }
 
+static int pci_epf_alloc_doorbell_embedded(struct pci_epf *epf, u16 num_db)
+{
+	const struct pci_epc_aux_resource *doorbell = NULL;
+	struct pci_epf_doorbell_msg *msg;
+	struct pci_epc *epc = epf->epc;
+	size_t map_size = 0, off = 0;
+	dma_addr_t iova_base = 0;
+	phys_addr_t phys_base;
+	int count, ret, i;
+	u64 addr;
+
+	ret = pci_epc_count_aux_resources(epc, epf->func_no, epf->vfunc_no,
+					  &count);
+	if (ret == -EOPNOTSUPP)
+		return -ENODEV;
+	if (ret)
+		return ret;
+	if (!count)
+		return -ENODEV;
+
+	struct pci_epc_aux_resource *res __free(kfree) =
+				kcalloc(count, sizeof(*res), GFP_KERNEL);
+	if (!res)
+		return -ENOMEM;
+
+	ret = pci_epc_get_aux_resources(epc, epf->func_no, epf->vfunc_no,
+					res, count);
+	if (ret == -EOPNOTSUPP)
+		return -ENODEV;
+	if (ret)
+		return ret;
+
+	/* TODO: Support multiple DOORBELL_MMIO resources per EPC. */
+	for (i = 0; i < count; i++) {
+		if (res[i].type != PCI_EPC_AUX_DOORBELL_MMIO)
+			continue;
+
+		doorbell = &res[i];
+		break;
+	}
+	if (!doorbell)
+		return -ENODEV;
+	addr = doorbell->phys_addr;
+	if (!IS_ALIGNED(addr, sizeof(u32)))
+		return -EINVAL;
+
+	/*
+	 * Reuse the pre-exposed BAR window if available. Otherwise map the MMIO
+	 * doorbell resource here. Any required IOMMU mapping is handled
+	 * internally, matching the MSI doorbell semantics.
+	 */
+	if (doorbell->bar == NO_BAR) {
+		phys_base = addr & PAGE_MASK;
+		off = addr - phys_base;
+		map_size = PAGE_ALIGN(off + sizeof(u32));
+
+		iova_base = dma_map_resource(epc->dev.parent, phys_base,
+					     map_size, DMA_FROM_DEVICE, 0);
+		if (dma_mapping_error(epc->dev.parent, iova_base))
+			return -EIO;
+
+		addr = iova_base + off;
+	}
+
+	msg = kcalloc(num_db, sizeof(*msg), GFP_KERNEL);
+	if (!msg) {
+		ret = -ENOMEM;
+		goto err_unmap;
+	}
+
+	/*
+	 * Embedded doorbell backends (e.g. DesignWare eDMA interrupt emulation)
+	 * typically provide a single IRQ and do not offer per-doorbell
+	 * distinguishable address/data pairs. The EPC aux resource therefore
+	 * exposes one DOORBELL_MMIO entry (u.db_mmio.irq).
+	 *
+	 * Still, pci_epf_alloc_doorbell() allows requesting multiple doorbells.
+	 * For such backends we replicate the same address/data for each entry
+	 * and mark the IRQ as shared (IRQF_SHARED). Consumers must treat them
+	 * as equivalent "kick" doorbells.
+	 */
+	for (i = 0; i < num_db; i++)
+		msg[i] = (struct pci_epf_doorbell_msg) {
+			.msg.address_lo = (u32)addr,
+			.msg.address_hi = (u32)(addr >> 32),
+			.msg.data = doorbell->u.db_mmio.data,
+			.virq = doorbell->u.db_mmio.irq,
+			.irq_flags = IRQF_SHARED,
+			.type = PCI_EPF_DOORBELL_EMBEDDED,
+			.bar = doorbell->bar,
+			.offset = (doorbell->bar == NO_BAR) ? 0 :
+				  doorbell->bar_offset,
+			.iova_base = iova_base,
+			.iova_size = map_size,
+		};
+
+	epf->num_db = num_db;
+	epf->db_msg = msg;
+	return 0;
+
+err_unmap:
+	if (map_size)
+		dma_unmap_resource(epc->dev.parent, iova_base, map_size,
+				   DMA_FROM_DEVICE, 0);
+	return ret;
+}
+
 static int pci_epf_alloc_doorbell_msi(struct pci_epf *epf, u16 num_db)
 {
 	struct pci_epf_doorbell_msg *msg;
@@ -109,18 +218,38 @@ int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
 	if (!ret)
 		return 0;
 
-	dev_err(dev, "Failed to allocate doorbell: %d\n", ret);
-	return ret;
+	/*
+	 * Fall back to embedded doorbell only when platform MSI is unavailable
+	 * for this EPC.
+	 */
+	if (ret != -ENODEV)
+		return ret;
+
+	ret = pci_epf_alloc_doorbell_embedded(epf, num_db);
+	if (ret) {
+		dev_err(dev, "Failed to allocate doorbell: %d\n", ret);
+		return ret;
+	}
+
+	dev_info(dev, "Using embedded (DMA) doorbell fallback\n");
+	return 0;
 }
 EXPORT_SYMBOL_GPL(pci_epf_alloc_doorbell);
 
 void pci_epf_free_doorbell(struct pci_epf *epf)
 {
+	struct pci_epf_doorbell_msg *msg0;
+	struct pci_epc *epc = epf->epc;
+
 	if (!epf->db_msg)
 		return;
 
-	if (epf->db_msg[0].type == PCI_EPF_DOORBELL_MSI)
+	msg0 = &epf->db_msg[0];
+	if (msg0->type == PCI_EPF_DOORBELL_MSI)
 		platform_device_msi_free_irqs_all(epf->epc->dev.parent);
+	else if (msg0->type == PCI_EPF_DOORBELL_EMBEDDED && msg0->iova_size)
+		dma_unmap_resource(epc->dev.parent, msg0->iova_base,
+				   msg0->iova_size, DMA_FROM_DEVICE, 0);
 
 	kfree(epf->db_msg);
 	epf->db_msg = NULL;
diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
index cd747447a1ea..8a6c64a35890 100644
--- a/include/linux/pci-epf.h
+++ b/include/linux/pci-epf.h
@@ -171,6 +171,12 @@ enum pci_epf_doorbell_type {
  *       (NO_BAR if not)
  * @offset: offset within @bar for the doorbell target (valid iff
  *          @bar != NO_BAR)
+ * @iova_base: Internal: base DMA address returned by dma_map_resource() for the
+ *             embedded doorbell MMIO window (used only for unmapping). Valid
+ *             when @type is PCI_EPF_DOORBELL_EMBEDDED and @iova_size is
+ *             non-zero.
+ * @iova_size: Internal: size of the dma_map_resource() mapping at @iova_base.
+ *             Zero when no mapping was created (e.g. pre-exposed fixed BAR).
  */
 struct pci_epf_doorbell_msg {
 	struct msi_msg msg;
@@ -179,6 +185,8 @@ struct pci_epf_doorbell_msg {
 	enum pci_epf_doorbell_type type;
 	enum pci_barno bar;
 	resource_size_t offset;
+	dma_addr_t iova_base;
+	size_t iova_size;
 };
 
 /**
-- 
2.51.0

Re: [PATCH v12 1/7] PCI: endpoint: Add auxiliary resource query API

[Frank Li]

On Fri, Mar 27, 2026 at 12:54:16PM +0900, Koichiro Den wrote:
> Endpoint controller drivers may integrate auxiliary blocks (e.g. DMA
> engines) whose register windows and descriptor memories metadata need to
> be exposed to a remote peer. Endpoint function drivers need a generic
> way to discover such resources without hard-coding controller-specific
> helpers.
>
> Add pci_epc_count_aux_resources() / pci_epc_get_aux_resources() and the
> corresponding pci_epc_ops callbacks. The count helper returns the number
> of available resources via an output parameter, while the get helper
> fills a caller-provided array of resources described by type, physical
> address and size, plus type-specific metadata.
>
> Suggested-by: Manivannan Sadhasivam <mani@kernel.org>
> Signed-off-by: Koichiro Den <den@valinux.co.jp>
> ---
> Changes in v12:
>   - Add pci_epc_count_aux_resources() and pci_epc_ops.count_aux_resources
>   - Use pci_epc_function_is_valid() instead of open-coding
>
>  drivers/pci/endpoint/pci-epc-core.c | 83 +++++++++++++++++++++++++++++
>  include/linux/pci-epc.h             | 53 ++++++++++++++++++
>  2 files changed, 136 insertions(+)
>
> diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> index 6c3c58185fc5..fded71a19d71 100644
> --- a/drivers/pci/endpoint/pci-epc-core.c
> +++ b/drivers/pci/endpoint/pci-epc-core.c
> @@ -156,6 +156,89 @@ const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
>  }
>  EXPORT_SYMBOL_GPL(pci_epc_get_features);
>
> +/**
> + * pci_epc_count_aux_resources() - count EPC-provided auxiliary resources
> + * @epc: EPC device
> + * @func_no: function number
> + * @vfunc_no: virtual function number
> + * @num_resources: returned number of auxiliary resources
> + *
> + * Some EPC backends integrate auxiliary blocks (e.g. DMA engines) whose control
> + * registers and/or descriptor memories can be exposed to the host by mapping
> + * them into BAR space. This helper queries how many such resources the backend
> + * provides.
> + *
> + * Return: 0 on success, -EOPNOTSUPP if the backend does not support auxiliary
> + * resource queries, or another -errno on failure.
> + */
> +int pci_epc_count_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> +				int *num_resources)

Most like such kinds APIs return count directly,
  < 0,  means error.
 >= 0,  means how many resource.

Frank

Re: [PATCH v12 1/7] PCI: endpoint: Add auxiliary resource query API

[Koichiro Den]

On Fri, Mar 27, 2026 at 12:31:09PM -0400, Frank Li wrote:
> On Fri, Mar 27, 2026 at 12:54:16PM +0900, Koichiro Den wrote:
> > Endpoint controller drivers may integrate auxiliary blocks (e.g. DMA
> > engines) whose register windows and descriptor memories metadata need to
> > be exposed to a remote peer. Endpoint function drivers need a generic
> > way to discover such resources without hard-coding controller-specific
> > helpers.
> >
> > Add pci_epc_count_aux_resources() / pci_epc_get_aux_resources() and the
> > corresponding pci_epc_ops callbacks. The count helper returns the number
> > of available resources via an output parameter, while the get helper
> > fills a caller-provided array of resources described by type, physical
> > address and size, plus type-specific metadata.
> >
> > Suggested-by: Manivannan Sadhasivam <mani@kernel.org>
> > Signed-off-by: Koichiro Den <den@valinux.co.jp>
> > ---
> > Changes in v12:
> >   - Add pci_epc_count_aux_resources() and pci_epc_ops.count_aux_resources
> >   - Use pci_epc_function_is_valid() instead of open-coding
> >
> >  drivers/pci/endpoint/pci-epc-core.c | 83 +++++++++++++++++++++++++++++
> >  include/linux/pci-epc.h             | 53 ++++++++++++++++++
> >  2 files changed, 136 insertions(+)
> >
> > diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> > index 6c3c58185fc5..fded71a19d71 100644
> > --- a/drivers/pci/endpoint/pci-epc-core.c
> > +++ b/drivers/pci/endpoint/pci-epc-core.c
> > @@ -156,6 +156,89 @@ const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
> >  }
> >  EXPORT_SYMBOL_GPL(pci_epc_get_features);
> >
> > +/**
> > + * pci_epc_count_aux_resources() - count EPC-provided auxiliary resources
> > + * @epc: EPC device
> > + * @func_no: function number
> > + * @vfunc_no: virtual function number
> > + * @num_resources: returned number of auxiliary resources
> > + *
> > + * Some EPC backends integrate auxiliary blocks (e.g. DMA engines) whose control
> > + * registers and/or descriptor memories can be exposed to the host by mapping
> > + * them into BAR space. This helper queries how many such resources the backend
> > + * provides.
> > + *
> > + * Return: 0 on success, -EOPNOTSUPP if the backend does not support auxiliary
> > + * resource queries, or another -errno on failure.
> > + */
> > +int pci_epc_count_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> > +				int *num_resources)
> 
> Most like such kinds APIs return count directly,
>   < 0,  means error.
>  >= 0,  means how many resource.

I chose to return 0 on success here based on Mani's earlier feedback on v11:
https://lore.kernel.org/linux-pci/lfbv6sjevz4xtjr6zt2hl3wap3bfwkvigqb6fdztqmutxgcvld@3t4x5gstr4nj/

I don't have a strong preference here, but since there seems to be no clear
policy/convention across the kernel, I would prefer to follow what is most
consistent and maintainable for the maintainers. Of course, I'm happy to switch
and respin if preferred.

Thanks for reviewing,
Koichiro

> 
> Frank

Re: [PATCH v12 1/7] PCI: endpoint: Add auxiliary resource query API

[Frank Li]

On Tue, Mar 31, 2026 at 10:56:34PM +0900, Koichiro Den wrote:
> On Fri, Mar 27, 2026 at 12:31:09PM -0400, Frank Li wrote:
> > On Fri, Mar 27, 2026 at 12:54:16PM +0900, Koichiro Den wrote:
> > > Endpoint controller drivers may integrate auxiliary blocks (e.g. DMA
> > > engines) whose register windows and descriptor memories metadata need to
> > > be exposed to a remote peer. Endpoint function drivers need a generic
> > > way to discover such resources without hard-coding controller-specific
> > > helpers.
> > >
> > > Add pci_epc_count_aux_resources() / pci_epc_get_aux_resources() and the
> > > corresponding pci_epc_ops callbacks. The count helper returns the number
> > > of available resources via an output parameter, while the get helper
> > > fills a caller-provided array of resources described by type, physical
> > > address and size, plus type-specific metadata.
> > >
> > > Suggested-by: Manivannan Sadhasivam <mani@kernel.org>
> > > Signed-off-by: Koichiro Den <den@valinux.co.jp>
> > > ---
> > > Changes in v12:
> > >   - Add pci_epc_count_aux_resources() and pci_epc_ops.count_aux_resources
> > >   - Use pci_epc_function_is_valid() instead of open-coding
> > >
> > >  drivers/pci/endpoint/pci-epc-core.c | 83 +++++++++++++++++++++++++++++
> > >  include/linux/pci-epc.h             | 53 ++++++++++++++++++
> > >  2 files changed, 136 insertions(+)
> > >
> > > diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> > > index 6c3c58185fc5..fded71a19d71 100644
> > > --- a/drivers/pci/endpoint/pci-epc-core.c
> > > +++ b/drivers/pci/endpoint/pci-epc-core.c
> > > @@ -156,6 +156,89 @@ const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
> > >  }
> > >  EXPORT_SYMBOL_GPL(pci_epc_get_features);
> > >
> > > +/**
> > > + * pci_epc_count_aux_resources() - count EPC-provided auxiliary resources
> > > + * @epc: EPC device
> > > + * @func_no: function number
> > > + * @vfunc_no: virtual function number
> > > + * @num_resources: returned number of auxiliary resources
> > > + *
> > > + * Some EPC backends integrate auxiliary blocks (e.g. DMA engines) whose control
> > > + * registers and/or descriptor memories can be exposed to the host by mapping
> > > + * them into BAR space. This helper queries how many such resources the backend
> > > + * provides.
> > > + *
> > > + * Return: 0 on success, -EOPNOTSUPP if the backend does not support auxiliary
> > > + * resource queries, or another -errno on failure.
> > > + */
> > > +int pci_epc_count_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> > > +				int *num_resources)
> >
> > Most like such kinds APIs return count directly,
> >   < 0,  means error.
> >  >= 0,  means how many resource.
>
> I chose to return 0 on success here based on Mani's earlier feedback on v11:
> https://lore.kernel.org/linux-pci/lfbv6sjevz4xtjr6zt2hl3wap3bfwkvigqb6fdztqmutxgcvld@3t4x5gstr4nj/

I am okay for both, But may request Mani think 2nd. Most existing kernel
API use return value for count of resource.

Frank
>
> I don't have a strong preference here, but since there seems to be no clear
> policy/convention across the kernel, I would prefer to follow what is most
> consistent and maintainable for the maintainers. Of course, I'm happy to switch
> and respin if preferred.
>
> Thanks for reviewing,
> Koichiro
>
> >
> > Frank

Re: [PATCH v12 1/7] PCI: endpoint: Add auxiliary resource query API

[Manivannan Sadhasivam]

On Tue, Mar 31, 2026 at 10:09:28AM -0400, Frank Li wrote:
> On Tue, Mar 31, 2026 at 10:56:34PM +0900, Koichiro Den wrote:
> > On Fri, Mar 27, 2026 at 12:31:09PM -0400, Frank Li wrote:
> > > On Fri, Mar 27, 2026 at 12:54:16PM +0900, Koichiro Den wrote:
> > > > Endpoint controller drivers may integrate auxiliary blocks (e.g. DMA
> > > > engines) whose register windows and descriptor memories metadata need to
> > > > be exposed to a remote peer. Endpoint function drivers need a generic
> > > > way to discover such resources without hard-coding controller-specific
> > > > helpers.
> > > >
> > > > Add pci_epc_count_aux_resources() / pci_epc_get_aux_resources() and the
> > > > corresponding pci_epc_ops callbacks. The count helper returns the number
> > > > of available resources via an output parameter, while the get helper
> > > > fills a caller-provided array of resources described by type, physical
> > > > address and size, plus type-specific metadata.
> > > >
> > > > Suggested-by: Manivannan Sadhasivam <mani@kernel.org>
> > > > Signed-off-by: Koichiro Den <den@valinux.co.jp>
> > > > ---
> > > > Changes in v12:
> > > >   - Add pci_epc_count_aux_resources() and pci_epc_ops.count_aux_resources
> > > >   - Use pci_epc_function_is_valid() instead of open-coding
> > > >
> > > >  drivers/pci/endpoint/pci-epc-core.c | 83 +++++++++++++++++++++++++++++
> > > >  include/linux/pci-epc.h             | 53 ++++++++++++++++++
> > > >  2 files changed, 136 insertions(+)
> > > >
> > > > diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> > > > index 6c3c58185fc5..fded71a19d71 100644
> > > > --- a/drivers/pci/endpoint/pci-epc-core.c
> > > > +++ b/drivers/pci/endpoint/pci-epc-core.c
> > > > @@ -156,6 +156,89 @@ const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
> > > >  }
> > > >  EXPORT_SYMBOL_GPL(pci_epc_get_features);
> > > >
> > > > +/**
> > > > + * pci_epc_count_aux_resources() - count EPC-provided auxiliary resources
> > > > + * @epc: EPC device
> > > > + * @func_no: function number
> > > > + * @vfunc_no: virtual function number
> > > > + * @num_resources: returned number of auxiliary resources
> > > > + *
> > > > + * Some EPC backends integrate auxiliary blocks (e.g. DMA engines) whose control
> > > > + * registers and/or descriptor memories can be exposed to the host by mapping
> > > > + * them into BAR space. This helper queries how many such resources the backend
> > > > + * provides.
> > > > + *
> > > > + * Return: 0 on success, -EOPNOTSUPP if the backend does not support auxiliary
> > > > + * resource queries, or another -errno on failure.
> > > > + */
> > > > +int pci_epc_count_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> > > > +				int *num_resources)
> > >
> > > Most like such kinds APIs return count directly,
> > >   < 0,  means error.
> > >  >= 0,  means how many resource.
> >
> > I chose to return 0 on success here based on Mani's earlier feedback on v11:
> > https://lore.kernel.org/linux-pci/lfbv6sjevz4xtjr6zt2hl3wap3bfwkvigqb6fdztqmutxgcvld@3t4x5gstr4nj/
> 
> I am okay for both, But may request Mani think 2nd. Most existing kernel
> API use return value for count of resource.
> 

Ok, fine with me.

@Koichiro Den: When you respin, could you please rename the API to
pci_epc_get_aux_resources_count()?

Reset LGTM!

- Mani

-- 
மணிவண்ணன் சதாசிவம்

Re: [PATCH v12 1/7] PCI: endpoint: Add auxiliary resource query API

[Koichiro Den]

On Fri, Apr 03, 2026 at 10:25:04PM +0530, Manivannan Sadhasivam wrote:
> On Tue, Mar 31, 2026 at 10:09:28AM -0400, Frank Li wrote:
> > On Tue, Mar 31, 2026 at 10:56:34PM +0900, Koichiro Den wrote:
> > > On Fri, Mar 27, 2026 at 12:31:09PM -0400, Frank Li wrote:
> > > > On Fri, Mar 27, 2026 at 12:54:16PM +0900, Koichiro Den wrote:
> > > > > Endpoint controller drivers may integrate auxiliary blocks (e.g. DMA
> > > > > engines) whose register windows and descriptor memories metadata need to
> > > > > be exposed to a remote peer. Endpoint function drivers need a generic
> > > > > way to discover such resources without hard-coding controller-specific
> > > > > helpers.
> > > > >
> > > > > Add pci_epc_count_aux_resources() / pci_epc_get_aux_resources() and the
> > > > > corresponding pci_epc_ops callbacks. The count helper returns the number
> > > > > of available resources via an output parameter, while the get helper
> > > > > fills a caller-provided array of resources described by type, physical
> > > > > address and size, plus type-specific metadata.
> > > > >
> > > > > Suggested-by: Manivannan Sadhasivam <mani@kernel.org>
> > > > > Signed-off-by: Koichiro Den <den@valinux.co.jp>
> > > > > ---
> > > > > Changes in v12:
> > > > >   - Add pci_epc_count_aux_resources() and pci_epc_ops.count_aux_resources
> > > > >   - Use pci_epc_function_is_valid() instead of open-coding
> > > > >
> > > > >  drivers/pci/endpoint/pci-epc-core.c | 83 +++++++++++++++++++++++++++++
> > > > >  include/linux/pci-epc.h             | 53 ++++++++++++++++++
> > > > >  2 files changed, 136 insertions(+)
> > > > >
> > > > > diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> > > > > index 6c3c58185fc5..fded71a19d71 100644
> > > > > --- a/drivers/pci/endpoint/pci-epc-core.c
> > > > > +++ b/drivers/pci/endpoint/pci-epc-core.c
> > > > > @@ -156,6 +156,89 @@ const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
> > > > >  }
> > > > >  EXPORT_SYMBOL_GPL(pci_epc_get_features);
> > > > >
> > > > > +/**
> > > > > + * pci_epc_count_aux_resources() - count EPC-provided auxiliary resources
> > > > > + * @epc: EPC device
> > > > > + * @func_no: function number
> > > > > + * @vfunc_no: virtual function number
> > > > > + * @num_resources: returned number of auxiliary resources
> > > > > + *
> > > > > + * Some EPC backends integrate auxiliary blocks (e.g. DMA engines) whose control
> > > > > + * registers and/or descriptor memories can be exposed to the host by mapping
> > > > > + * them into BAR space. This helper queries how many such resources the backend
> > > > > + * provides.
> > > > > + *
> > > > > + * Return: 0 on success, -EOPNOTSUPP if the backend does not support auxiliary
> > > > > + * resource queries, or another -errno on failure.
> > > > > + */
> > > > > +int pci_epc_count_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> > > > > +				int *num_resources)
> > > >
> > > > Most like such kinds APIs return count directly,
> > > >   < 0,  means error.
> > > >  >= 0,  means how many resource.
> > >
> > > I chose to return 0 on success here based on Mani's earlier feedback on v11:
> > > https://lore.kernel.org/linux-pci/lfbv6sjevz4xtjr6zt2hl3wap3bfwkvigqb6fdztqmutxgcvld@3t4x5gstr4nj/
> > 
> > I am okay for both, But may request Mani think 2nd. Most existing kernel
> > API use return value for count of resource.
> > 
> 
> Ok, fine with me.
> 
> @Koichiro Den: When you respin, could you please rename the API to
> pci_epc_get_aux_resources_count()?

Alright, thank you both!

Koichiro

> 
> Reset LGTM!
> 
> - Mani
> 
> -- 
> மணிவண்ணன் சதாசிவம்