[PATCH v12 19/25] cxl: Introduce cxl_pci_drv_bound() to check for bound driver

[Terry Bowman <terry.bowman@amd.com>]

CXL devices handle protocol errors via driver-specific callbacks rather
than the generic pci_driver::err_handlers by default. The callbacks are
implemented in the cxl_pci driver and are not part of struct pci_driver, so
cxl_core must verify that a device is actually bound to the cxl_pci
module's driver before invoking the callbacks (the device could be bound
to another driver, e.g. VFIO).

However, cxl_core can not reference symbols in the cxl_pci module because
it creates a circular dependency. This prevents cxl_core from checking the
EP's bound driver and calling the callbacks.

To fix this, move drivers/cxl/pci.c into drivers/cxl/core/pci_drv.c and
build it as part of the cxl_core module. Compile into cxl_core using
CXL_PCI and CXL_CORE Kconfig dependencies. This removes the standalone cxl_pci
module, consolidates the cxl_pci driver code into cxl_core, and eliminates
the circular dependency so cxl_core can safely perform bound-driver checks
and invoke the CXL PCI callbacks.

Introduce cxl_pci_drv_bound() to return boolean depending on if the PCI EP
parameter is bound to a CXL driver instance. This will be used in future
patch when dequeuing work from the kfifo.

Signed-off-by: Terry Bowman <terry.bowman@amd.com>

---

Changes in v11 -> v12:
- New patch
---
 drivers/cxl/Kconfig                   |  6 +++---
 drivers/cxl/Makefile                  |  2 --
 drivers/cxl/core/Makefile             |  1 +
 drivers/cxl/core/core.h               |  9 +++++++++
 drivers/cxl/{pci.c => core/pci_drv.c} | 16 ++++++++--------
 drivers/cxl/core/port.c               |  3 +++
 6 files changed, 24 insertions(+), 13 deletions(-)
 rename drivers/cxl/{pci.c => core/pci_drv.c} (99%)

diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig
index 028201e24523..9ee76bae02d5 100644
--- a/drivers/cxl/Kconfig
+++ b/drivers/cxl/Kconfig
@@ -20,7 +20,7 @@ menuconfig CXL_BUS
 if CXL_BUS
 
 config CXL_PCI
-	tristate "PCI manageability"
+	bool "PCI manageability"
 	default CXL_BUS
 	help
 	  The CXL specification defines a "CXL memory device" sub-class in the
@@ -29,12 +29,12 @@ config CXL_PCI
 	  memory to be mapped into the system address map (Host-managed Device
 	  Memory (HDM)).
 
-	  Say 'y/m' to enable a driver that will attach to CXL memory expander
+	  Say 'y' to enable a driver that will attach to CXL memory expander
 	  devices enumerated by the memory device class code for configuration
 	  and management primarily via the mailbox interface. See Chapter 2.3
 	  Type 3 CXL Device in the CXL 2.0 specification for more details.
 
-	  If unsure say 'm'.
+	  If unsure say 'y'.
 
 config CXL_MEM_RAW_COMMANDS
 	bool "RAW Command Interface for Memory Devices"
diff --git a/drivers/cxl/Makefile b/drivers/cxl/Makefile
index 2caa90fa4bf2..ff6add88b6ae 100644
--- a/drivers/cxl/Makefile
+++ b/drivers/cxl/Makefile
@@ -12,10 +12,8 @@ obj-$(CONFIG_CXL_PORT) += cxl_port.o
 obj-$(CONFIG_CXL_ACPI) += cxl_acpi.o
 obj-$(CONFIG_CXL_PMEM) += cxl_pmem.o
 obj-$(CONFIG_CXL_MEM) += cxl_mem.o
-obj-$(CONFIG_CXL_PCI) += cxl_pci.o
 
 cxl_port-y := port.o
 cxl_acpi-y := acpi.o
 cxl_pmem-y := pmem.o security.o
 cxl_mem-y := mem.o
-cxl_pci-y := pci.o
diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile
index b2930cc54f8b..91f43c3f2292 100644
--- a/drivers/cxl/core/Makefile
+++ b/drivers/cxl/core/Makefile
@@ -20,3 +20,4 @@ cxl_core-$(CONFIG_CXL_MCE) += mce.o
 cxl_core-$(CONFIG_CXL_FEATURES) += features.o
 cxl_core-$(CONFIG_CXL_EDAC_MEM_FEATURES) += edac.o
 cxl_core-$(CONFIG_CXL_RAS) += ras.o
+cxl_core-$(CONFIG_CXL_PCI) += pci_drv.o
diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
index 74c64d458f12..9ceff8acf844 100644
--- a/drivers/cxl/core/core.h
+++ b/drivers/cxl/core/core.h
@@ -202,4 +202,13 @@ int cxl_set_feature(struct cxl_mailbox *cxl_mbox, const uuid_t *feat_uuid,
 		    u16 *return_code);
 #endif
 
+#ifdef CONFIG_CXL_PCI
+bool cxl_pci_drv_bound(struct pci_dev *pdev);
+int cxl_pci_driver_init(void);
+void cxl_pci_driver_exit(void);
+#else
+static inline bool cxl_pci_drv_bound(struct pci_dev *pdev) { return false; };
+static inline int cxl_pci_driver_init(void) { return 0; }
+static inline void cxl_pci_driver_exit(void) { }
+#endif
 #endif /* __CXL_CORE_H__ */
diff --git a/drivers/cxl/pci.c b/drivers/cxl/core/pci_drv.c
similarity index 99%
rename from drivers/cxl/pci.c
rename to drivers/cxl/core/pci_drv.c
index 71fb8709081e..746b5017d336 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/core/pci_drv.c
@@ -1132,6 +1132,12 @@ static struct pci_driver cxl_pci_driver = {
 	},
 };
 
+bool cxl_pci_drv_bound(struct pci_dev *pdev)
+{
+	return (pdev->driver == &cxl_pci_driver);
+}
+EXPORT_SYMBOL_NS_GPL(cxl_pci_drv_bound, "CXL");
+
 #define CXL_EVENT_HDR_FLAGS_REC_SEVERITY GENMASK(1, 0)
 static void cxl_handle_cper_event(enum cxl_event_type ev_type,
 				  struct cxl_cper_event_rec *rec)
@@ -1178,7 +1184,7 @@ static void cxl_cper_work_fn(struct work_struct *work)
 }
 static DECLARE_WORK(cxl_cper_work, cxl_cper_work_fn);
 
-static int __init cxl_pci_driver_init(void)
+int __init cxl_pci_driver_init(void)
 {
 	int rc;
 
@@ -1193,15 +1199,9 @@ static int __init cxl_pci_driver_init(void)
 	return rc;
 }
 
-static void __exit cxl_pci_driver_exit(void)
+void cxl_pci_driver_exit(void)
 {
 	cxl_cper_unregister_work(&cxl_cper_work);
 	cancel_work_sync(&cxl_cper_work);
 	pci_unregister_driver(&cxl_pci_driver);
 }
-
-module_init(cxl_pci_driver_init);
-module_exit(cxl_pci_driver_exit);
-MODULE_DESCRIPTION("CXL: PCI manageability");
-MODULE_LICENSE("GPL v2");
-MODULE_IMPORT_NS("CXL");
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index bd4be046888a..56fa4ac33e8b 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -2502,6 +2502,8 @@ static __init int cxl_core_init(void)
 	if (rc)
 		goto err_ras;
 
+	cxl_pci_driver_init();
+
 	return 0;
 
 err_ras:
@@ -2517,6 +2519,7 @@ static __init int cxl_core_init(void)
 
 static void cxl_core_exit(void)
 {
+	cxl_pci_driver_exit();
 	cxl_ras_exit();
 	cxl_region_exit();
 	bus_unregister(&cxl_bus_type);
-- 
2.34.1