* [PATCH v11 1/1] mctp pcc: Implement MCTP over PCC Transport
2025-01-04 3:54 [PATCH v11 0/1] MCTP Over PCC Transport admiyo
@ 2025-01-04 3:54 ` admiyo
2025-01-06 1:05 ` [PATCH v11 0/1] MCTP Over " Jeremy Kerr
1 sibling, 0 replies; 4+ messages in thread
From: admiyo @ 2025-01-04 3:54 UTC (permalink / raw)
To: Jeremy Kerr, Matt Johnston, Andrew Lunn, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni
Cc: netdev, linux-kernel, Sudeep Holla, Jonathan Cameron, Huisong Li
From: Adam Young <admiyo@os.amperecomputing.com>
Implementation of network driver for
Management Control Transport Protocol(MCTP) over
Platform Communication Channel(PCC)
DMTF DSP:0292
https://www.dmtf.org/sites/default/files/standards/documents/DSP0292_1.0.0WIP50.pdf
MCTP devices are specified by entries in DSDT/SDST and
reference channels specified in the PCCT.
Communication with other devices use the PCC based
doorbell mechanism.
Signed-off-by: Adam Young <admiyo@os.amperecomputing.com>
---
drivers/net/mctp/Kconfig | 13 ++
drivers/net/mctp/Makefile | 1 +
drivers/net/mctp/mctp-pcc.c | 311 ++++++++++++++++++++++++++++++++++++
3 files changed, 325 insertions(+)
create mode 100644 drivers/net/mctp/mctp-pcc.c
diff --git a/drivers/net/mctp/Kconfig b/drivers/net/mctp/Kconfig
index 15860d6ac39f..073eb2a21841 100644
--- a/drivers/net/mctp/Kconfig
+++ b/drivers/net/mctp/Kconfig
@@ -47,6 +47,19 @@ config MCTP_TRANSPORT_I3C
A MCTP protocol network device is created for each I3C bus
having a "mctp-controller" devicetree property.
+config MCTP_TRANSPORT_PCC
+ tristate "MCTP PCC transport"
+ depends on ACPI
+ help
+ Provides a driver to access MCTP devices over PCC transport,
+ A MCTP protocol network device is created via ACPI for each
+ entry in the DST/SDST that matches the identifier. The Platform
+ communication channels are selected from the corresponding
+ entries in the PCCT.
+
+ Say y here if you need to connect to MCTP endpoints over PCC. To
+ compile as a module, use m; the module will be called mctp-pcc.
+
endmenu
endif
diff --git a/drivers/net/mctp/Makefile b/drivers/net/mctp/Makefile
index e1cb99ced54a..492a9e47638f 100644
--- a/drivers/net/mctp/Makefile
+++ b/drivers/net/mctp/Makefile
@@ -1,3 +1,4 @@
+obj-$(CONFIG_MCTP_TRANSPORT_PCC) += mctp-pcc.o
obj-$(CONFIG_MCTP_SERIAL) += mctp-serial.o
obj-$(CONFIG_MCTP_TRANSPORT_I2C) += mctp-i2c.o
obj-$(CONFIG_MCTP_TRANSPORT_I3C) += mctp-i3c.o
diff --git a/drivers/net/mctp/mctp-pcc.c b/drivers/net/mctp/mctp-pcc.c
new file mode 100644
index 000000000000..4cd66c0ded85
--- /dev/null
+++ b/drivers/net/mctp/mctp-pcc.c
@@ -0,0 +1,311 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * mctp-pcc.c - Driver for MCTP over PCC.
+ * Copyright (c) 2024, Ampere Computing LLC
+ */
+
+/* Implementation of MCTP over PCC DMTF Specification DSP0256
+ * https://www.dmtf.org/sites/default/files/standards/documents/DSP0256_2.0.0WIP50.pdf
+ */
+
+#include <linux/acpi.h>
+#include <linux/if_arp.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/platform_device.h>
+#include <linux/string.h>
+
+#include <acpi/acpi_bus.h>
+#include <acpi/acpi_drivers.h>
+#include <acpi/acrestyp.h>
+#include <acpi/actbl.h>
+#include <net/mctp.h>
+#include <net/mctpdevice.h>
+#include <acpi/pcc.h>
+
+#define MCTP_PAYLOAD_LENGTH 256
+#define MCTP_CMD_LENGTH 4
+#define MCTP_PCC_VERSION 0x1 /* DSP0253 defines a single version: 1 */
+#define MCTP_SIGNATURE "MCTP"
+#define MCTP_SIGNATURE_LENGTH (sizeof(MCTP_SIGNATURE) - 1)
+#define MCTP_HEADER_LENGTH 12
+#define MCTP_MIN_MTU 68
+#define PCC_MAGIC 0x50434300
+#define PCC_HEADER_FLAG_REQ_INT 0x1
+#define PCC_HEADER_FLAGS PCC_HEADER_FLAG_REQ_INT
+#define PCC_DWORD_TYPE 0x0c
+
+struct mctp_pcc_hdr {
+ u32 signature;
+ u32 flags;
+ u32 length;
+ char mctp_signature[MCTP_SIGNATURE_LENGTH];
+};
+
+struct mctp_pcc_mailbox {
+ u32 index;
+ struct pcc_mbox_chan *chan;
+ struct mbox_client client;
+};
+
+/* The netdev structure. One of these per PCC adapter. */
+struct mctp_pcc_ndev {
+ /* spinlock to serialize access to PCC outbox buffer and registers
+ * Note that what PCC calls registers are memory locations, not CPU
+ * Registers. They include the fields used to synchronize access
+ * between the OS and remote endpoints.
+ *
+ * Only the Outbox needs a spinlock, to prevent multiple
+ * sent packets triggering multiple attempts to over write
+ * the outbox. The Inbox buffer is controlled by the remote
+ * service and a spinlock would have no effect.
+ */
+ spinlock_t lock;
+ struct mctp_dev mdev;
+ struct acpi_device *acpi_device;
+ struct mctp_pcc_mailbox inbox;
+ struct mctp_pcc_mailbox outbox;
+};
+
+static void mctp_pcc_client_rx_callback(struct mbox_client *c, void *buffer)
+{
+ struct mctp_pcc_ndev *mctp_pcc_ndev;
+ struct mctp_pcc_hdr mctp_pcc_hdr;
+ struct mctp_skb_cb *cb;
+ struct sk_buff *skb;
+ void *skb_buf;
+ u32 data_len;
+
+ mctp_pcc_ndev = container_of(c, struct mctp_pcc_ndev, inbox.client);
+ memcpy_fromio(&mctp_pcc_hdr, mctp_pcc_ndev->inbox.chan->shmem,
+ sizeof(struct mctp_pcc_hdr));
+ data_len = mctp_pcc_hdr.length + MCTP_HEADER_LENGTH;
+ if (data_len > mctp_pcc_ndev->mdev.dev->mtu) {
+ dev_dstats_rx_dropped(mctp_pcc_ndev->mdev.dev);
+ return;
+ }
+
+ skb = netdev_alloc_skb(mctp_pcc_ndev->mdev.dev, data_len);
+ if (!skb) {
+ dev_dstats_rx_dropped(mctp_pcc_ndev->mdev.dev);
+ return;
+ }
+ dev_dstats_rx_add(mctp_pcc_ndev->mdev.dev, data_len);
+
+ skb->protocol = htons(ETH_P_MCTP);
+ skb_buf = skb_put(skb, data_len);
+ memcpy_fromio(skb_buf, mctp_pcc_ndev->inbox.chan->shmem, data_len);
+
+ skb_reset_mac_header(skb);
+ skb_pull(skb, sizeof(struct mctp_pcc_hdr));
+ skb_reset_network_header(skb);
+ cb = __mctp_cb(skb);
+ cb->halen = 0;
+ netif_rx(skb);
+}
+
+static netdev_tx_t mctp_pcc_tx(struct sk_buff *skb, struct net_device *ndev)
+{
+ struct mctp_pcc_ndev *mpnd = netdev_priv(ndev);
+ struct mctp_pcc_hdr *mctp_pcc_header;
+ void __iomem *buffer;
+ unsigned long flags;
+ int len = skb->len;
+
+ dev_dstats_tx_add(ndev, len);
+
+ spin_lock_irqsave(&mpnd->lock, flags);
+ mctp_pcc_header = skb_push(skb, sizeof(struct mctp_pcc_hdr));
+ buffer = mpnd->outbox.chan->shmem;
+ mctp_pcc_header->signature = PCC_MAGIC | mpnd->outbox.index;
+ mctp_pcc_header->flags = PCC_HEADER_FLAGS;
+ memcpy(mctp_pcc_header->mctp_signature, MCTP_SIGNATURE,
+ MCTP_SIGNATURE_LENGTH);
+ mctp_pcc_header->length = len + MCTP_SIGNATURE_LENGTH;
+
+ memcpy_toio(buffer, skb->data, skb->len);
+ mpnd->outbox.chan->mchan->mbox->ops->send_data(mpnd->outbox.chan->mchan,
+ NULL);
+ spin_unlock_irqrestore(&mpnd->lock, flags);
+
+ dev_consume_skb_any(skb);
+ return NETDEV_TX_OK;
+}
+
+static const struct net_device_ops mctp_pcc_netdev_ops = {
+ .ndo_start_xmit = mctp_pcc_tx,
+};
+
+static const struct mctp_netdev_ops mctp_netdev_ops = {
+ NULL
+};
+
+static void mctp_pcc_setup(struct net_device *ndev)
+{
+ ndev->type = ARPHRD_MCTP;
+ ndev->hard_header_len = 0;
+ ndev->tx_queue_len = 0;
+ ndev->flags = IFF_NOARP;
+ ndev->netdev_ops = &mctp_pcc_netdev_ops;
+ ndev->needs_free_netdev = true;
+ ndev->pcpu_stat_type = NETDEV_PCPU_STAT_DSTATS;
+}
+
+struct mctp_pcc_lookup_context {
+ int index;
+ u32 inbox_index;
+ u32 outbox_index;
+};
+
+static acpi_status lookup_pcct_indices(struct acpi_resource *ares,
+ void *context)
+{
+ struct mctp_pcc_lookup_context *luc = context;
+ struct acpi_resource_address32 *addr;
+
+ switch (ares->type) {
+ case PCC_DWORD_TYPE:
+ break;
+ default:
+ return AE_OK;
+ }
+
+ addr = ACPI_CAST_PTR(struct acpi_resource_address32, &ares->data);
+ switch (luc->index) {
+ case 0:
+ luc->outbox_index = addr[0].address.minimum;
+ break;
+ case 1:
+ luc->inbox_index = addr[0].address.minimum;
+ break;
+ }
+ luc->index++;
+ return AE_OK;
+}
+
+static void mctp_cleanup_netdev(void *data)
+{
+ struct net_device *ndev = data;
+
+ mctp_unregister_netdev(ndev);
+}
+
+static void mctp_cleanup_channel(void *data)
+{
+ struct pcc_mbox_chan *chan = data;
+
+ pcc_mbox_free_channel(chan);
+}
+
+static int mctp_pcc_initialize_mailbox(struct device *dev,
+ struct mctp_pcc_mailbox *box, u32 index)
+{
+ int ret;
+
+ box->index = index;
+ box->chan = pcc_mbox_request_channel(&box->client, index);
+ if (IS_ERR(box->chan))
+ return PTR_ERR(box->chan);
+ devm_add_action_or_reset(dev, mctp_cleanup_channel, box->chan);
+ ret = pcc_mbox_ioremap(box->chan->mchan);
+ if (ret)
+ return -EINVAL;
+ return 0;
+}
+
+static int mctp_pcc_driver_add(struct acpi_device *acpi_dev)
+{
+ struct mctp_pcc_lookup_context context = {0, 0, 0};
+ struct mctp_pcc_ndev *mctp_pcc_ndev;
+ struct device *dev = &acpi_dev->dev;
+ struct net_device *ndev;
+ acpi_handle dev_handle;
+ acpi_status status;
+ int mctp_pcc_mtu;
+ char name[32];
+ int rc;
+
+ dev_dbg(dev, "Adding mctp_pcc device for HID %s\n",
+ acpi_device_hid(acpi_dev));
+ dev_handle = acpi_device_handle(acpi_dev);
+ status = acpi_walk_resources(dev_handle, "_CRS", lookup_pcct_indices,
+ &context);
+ if (!ACPI_SUCCESS(status)) {
+ dev_err(dev, "FAILURE to lookup PCC indexes from CRS\n");
+ return -EINVAL;
+ }
+
+ //inbox initialization
+ snprintf(name, sizeof(name), "mctpipcc%d", context.inbox_index);
+ ndev = alloc_netdev(sizeof(struct mctp_pcc_ndev), name, NET_NAME_ENUM,
+ mctp_pcc_setup);
+ if (!ndev)
+ return -ENOMEM;
+
+ mctp_pcc_ndev = netdev_priv(ndev);
+ rc = devm_add_action_or_reset(dev, mctp_cleanup_netdev, ndev);
+ if (rc)
+ goto cleanup_netdev;
+ spin_lock_init(&mctp_pcc_ndev->lock);
+
+ rc = mctp_pcc_initialize_mailbox(dev, &mctp_pcc_ndev->inbox,
+ context.inbox_index);
+ if (rc)
+ goto cleanup_netdev;
+ mctp_pcc_ndev->inbox.client.rx_callback = mctp_pcc_client_rx_callback;
+
+ //outbox initialization
+ rc = mctp_pcc_initialize_mailbox(dev, &mctp_pcc_ndev->outbox,
+ context.outbox_index);
+ if (rc)
+ goto cleanup_netdev;
+
+ mctp_pcc_ndev->acpi_device = acpi_dev;
+ mctp_pcc_ndev->inbox.client.dev = dev;
+ mctp_pcc_ndev->outbox.client.dev = dev;
+ mctp_pcc_ndev->mdev.dev = ndev;
+ acpi_dev->driver_data = mctp_pcc_ndev;
+
+ /* There is no clean way to pass the MTU to the callback function
+ * used for registration, so set the values ahead of time.
+ */
+ mctp_pcc_mtu = mctp_pcc_ndev->outbox.chan->shmem_size -
+ sizeof(struct mctp_pcc_hdr);
+ ndev->mtu = MCTP_MIN_MTU;
+ ndev->max_mtu = mctp_pcc_mtu;
+ ndev->min_mtu = MCTP_MIN_MTU;
+
+ /* ndev needs to be freed before the iomemory (mapped above) gets
+ * unmapped, devm resources get freed in reverse to the order they
+ * are added.
+ */
+ rc = mctp_register_netdev(ndev, &mctp_netdev_ops, MCTP_PHYS_BINDING_PCC);
+ return rc;
+cleanup_netdev:
+ free_netdev(ndev);
+ return rc;
+}
+
+static const struct acpi_device_id mctp_pcc_device_ids[] = {
+ { "DMT0001"},
+ {}
+};
+
+static struct acpi_driver mctp_pcc_driver = {
+ .name = "mctp_pcc",
+ .class = "Unknown",
+ .ids = mctp_pcc_device_ids,
+ .ops = {
+ .add = mctp_pcc_driver_add,
+ },
+};
+
+module_acpi_driver(mctp_pcc_driver);
+
+MODULE_DEVICE_TABLE(acpi, mctp_pcc_device_ids);
+
+MODULE_DESCRIPTION("MCTP PCC ACPI device");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Adam Young <admiyo@os.amperecomputing.com>");
--
2.43.0
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v11 0/1] MCTP Over PCC Transport
2025-01-04 3:54 [PATCH v11 0/1] MCTP Over PCC Transport admiyo
2025-01-04 3:54 ` [PATCH v11 1/1] mctp pcc: Implement MCTP over " admiyo
@ 2025-01-06 1:05 ` Jeremy Kerr
2025-01-06 17:30 ` Adam Young
1 sibling, 1 reply; 4+ messages in thread
From: Jeremy Kerr @ 2025-01-06 1:05 UTC (permalink / raw)
To: admiyo
Cc: netdev, linux-kernel, Matt Johnston, David S . Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, Sudeep Holla,
Jonathan Cameron, Huisong Li
Hi Adam,
> Changes in V11:
> - Switch Big Endian data types to machine local for PCC header
This seems suspicious; the concept of "machine local" may not be
consistent between channel endpoints (ie, system firmware and this
driver). Looking at DSP0292, and the PCC channel spec, it looks like
these should be explicitly little-endian, no?
The warnings you were seeing in v10 seemed to be an issue of direct
accesses to the __be32 types in struct mctp_pcc_hdr - ie., without
be32_to_cpu() accessors. If you keep the endian-annotated types (but
__le32 instead), and use the appropriate le32_to_cpu() accessors, that
should address those warnings, while keeping the driver endian-safe.
Cheers,
Jeremy
^ permalink raw reply [flat|nested] 4+ messages in thread