[PATCH v9 1/1] mctp pcc: Implement MCTP over PCC Transport

admiyo
2024-12-17T18:25:39Z

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 | 320 ++++++++++++++++++++++++++++++++++++
3 files changed, 334 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..6a29b164f208
--- /dev/null
+++ b/drivers/net/mctp/mctp-pcc.c
@@ -0,0 +1,320 @@
+// 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 {
+ __be32 signature;
+ __be32 flags;
+ __be32 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 pcpu_dstats *dstats;
+ 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;
+ skb = netdev_alloc_skb(mctp_pcc_ndev->mdev.dev, data_len);
+
+ dstats = this_cpu_ptr(mctp_pcc_ndev->mdev.dev->dstats);
+ u64_stats_update_begin(&dstats->syncp);
+ if (data_len > mctp_pcc_ndev->mdev.dev->mtu) {
+ u64_stats_inc(&dstats->rx_drops);
+ u64_stats_inc(&dstats->rx_drops);
+ u64_stats_update_end(&dstats->syncp);
+ return;
+ }
+ if (!skb) {
+ u64_stats_inc(&dstats->rx_drops);
+ u64_stats_update_end(&dstats->syncp);
+ return;
+ }
+ u64_stats_inc(&dstats->rx_packets);
+ u64_stats_add(&dstats->rx_bytes, data_len);
+ u64_stats_update_end(&dstats->syncp);
+
+ 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;
+ struct pcpu_dstats *dstats;
+ void __iomem *buffer;
+ unsigned long flags;
+ int len = skb->len;
+
+ dstats = this_cpu_ptr(ndev->dstats);
+ u64_stats_update_begin(&dstats->syncp);
+ u64_stats_inc(&dstats->tx_packets);
+ u64_stats_add(&dstats->tx_bytes, skb->len);
+ u64_stats_update_end(&dstats->syncp);
+
+ 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 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 = register_netdev(ndev);
+ 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