@@ -0,0 +1,323 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * mctp-pcc.c - Driver for MCTP over PCC.
+ * Copyright (c) 2024-2025, Ampere Computing LLC
+ *
+ */
+
+/* Implementation of MCTP over PCC DMTF Specification DSP0256
+ * https://www.dmtf.org/sites/default/files/standards/documents/DSP0292_1.0.0WIP50.pdf
+ */
+
+#include <linux/acpi.h>
+#include <linux/hrtimer.h>
+#include <linux/if_arp.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mailbox_client.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/platform_device.h>
+#include <linux/skbuff.h>
+#include <linux/string.h>
+
+#include <acpi/acpi_bus.h>
+#include <acpi/acpi_drivers.h>
+#include <acpi/acrestyp.h>
+#include <acpi/actbl.h>
+#include <acpi/pcc.h>
+#include <net/mctp.h>
+#include <net/mctpdevice.h>
+
+#define MCTP_SIGNATURE "MCTP"
+#define MCTP_SIGNATURE_LENGTH (sizeof(MCTP_SIGNATURE) - 1)
+#define MCTP_MIN_MTU 68
+#define PCC_DWORD_TYPE 0x0c
+
+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 {
+ struct net_device *ndev;
+ 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 *cl, void *mssg)
+{
+ struct acpi_pcct_ext_pcc_shared_memory pcc_header;
+ struct mctp_pcc_ndev *mctp_pcc_ndev;
+ struct mctp_pcc_mailbox *inbox;
+ struct mctp_skb_cb *cb;
+ struct sk_buff *skb;
+ int size;
+
+ mctp_pcc_ndev = container_of(cl, struct mctp_pcc_ndev, inbox.client);
+ inbox = &mctp_pcc_ndev->inbox;
+ size = pcc_mbox_query_bytes_available(inbox->chan);
+ if (size == 0)
+ return;
+ skb = netdev_alloc_skb(mctp_pcc_ndev->ndev, size);
+ if (!skb) {
+ dev_dstats_rx_dropped(mctp_pcc_ndev->ndev);
+ return;
+ }
+ skb_put(skb, size);
+ skb->protocol = htons(ETH_P_MCTP);
+ pcc_mbox_read_from_buffer(inbox->chan, size, skb->data);
+ dev_dstats_rx_add(mctp_pcc_ndev->ndev, skb->len);
+ skb_reset_mac_header(skb);
+ skb_pull(skb, sizeof(pcc_header));
+ 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 acpi_pcct_ext_pcc_shared_memory *pcc_header;
+ struct mctp_pcc_ndev *mpnd = netdev_priv(ndev);
+ int len = skb->len;
+ int rc;
+
+ rc = skb_cow_head(skb, sizeof(*pcc_header));
+ if (rc) {
+ dev_dstats_tx_dropped(ndev);
+ kfree_skb(skb);
+ return NETDEV_TX_OK;
+ }
+
+ pcc_header = skb_push(skb, sizeof(*pcc_header));
+ pcc_header->signature = PCC_SIGNATURE | mpnd->outbox.index;
+ pcc_header->flags = PCC_CMD_COMPLETION_NOTIFY;
+ memcpy(&pcc_header->command, MCTP_SIGNATURE, MCTP_SIGNATURE_LENGTH);
+ pcc_header->length = len + MCTP_SIGNATURE_LENGTH;
+
+ rc = mbox_send_message(mpnd->outbox.chan->mchan, skb);
+ if (rc < 0) {
+ netif_stop_queue(ndev);
+ return NETDEV_TX_BUSY;
+ }
+
+ dev_dstats_tx_add(ndev, len);
+ return NETDEV_TX_OK;
+}
+
+static void mctp_pcc_tx_prepare(struct mbox_client *cl, void *mssg)
+{
+ struct mctp_pcc_ndev *mctp_pcc_ndev;
+ struct mctp_pcc_mailbox *outbox;
+ struct sk_buff *skb = mssg;
+ int len_sent;
+
+ mctp_pcc_ndev = container_of(cl, struct mctp_pcc_ndev, outbox.client);
+ outbox = &mctp_pcc_ndev->outbox;
+
+ if (!skb)
+ return;
+
+ len_sent = pcc_mbox_write_to_buffer(outbox->chan, skb->len, skb->data);
+ if (len_sent == 0)
+ netdev_info(mctp_pcc_ndev->ndev, "packet dropped");
+}
+
+static void mctp_pcc_tx_done(struct mbox_client *c, void *mssg, int r)
+{
+ struct mctp_pcc_ndev *mctp_pcc_ndev;
+ struct mctp_pcc_mailbox *outbox;
+ struct sk_buff *skb = mssg;
+
+ mctp_pcc_ndev = container_of(c, struct mctp_pcc_ndev, outbox.client);
+ outbox = container_of(c, struct mctp_pcc_mailbox, client);
+ dev_consume_skb_any(skb);
+ netif_wake_queue(mctp_pcc_ndev->ndev);
+}
+
+static int mctp_pcc_ndo_open(struct net_device *ndev)
+{
+ struct mctp_pcc_ndev *mctp_pcc_ndev = netdev_priv(ndev);
+ struct mctp_pcc_mailbox *outbox, *inbox;
+
+ outbox = &mctp_pcc_ndev->outbox;
+ inbox = &mctp_pcc_ndev->inbox;
+
+ outbox->chan = pcc_mbox_request_channel(&outbox->client, outbox->index);
+ if (IS_ERR(outbox->chan))
+ return PTR_ERR(outbox->chan);
+
+ inbox->client.rx_callback = mctp_pcc_client_rx_callback;
+ inbox->chan = pcc_mbox_request_channel(&inbox->client, inbox->index);
+ if (IS_ERR(inbox->chan)) {
+ pcc_mbox_free_channel(outbox->chan);
+ return PTR_ERR(inbox->chan);
+ }
+ return 0;
+}
+
+static int mctp_pcc_ndo_stop(struct net_device *ndev)
+{
+ struct mctp_pcc_ndev *mctp_pcc_ndev = netdev_priv(ndev);
+
+ pcc_mbox_free_channel(mctp_pcc_ndev->outbox.chan);
+ pcc_mbox_free_channel(mctp_pcc_ndev->inbox.chan);
+ return 0;
+}
+
+static const struct net_device_ops mctp_pcc_netdev_ops = {
+ .ndo_open = mctp_pcc_ndo_open,
+ .ndo_stop = mctp_pcc_ndo_stop,
+ .ndo_start_xmit = mctp_pcc_tx,
+};
+
+static void mctp_pcc_setup(struct net_device *ndev)
+{
+ ndev->type = ARPHRD_MCTP;
+ ndev->hard_header_len = sizeof(struct acpi_pcct_ext_pcc_shared_memory);
+ 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;
+
+ if (ares->type != PCC_DWORD_TYPE)
+ 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 int initialize_MTU(struct net_device *ndev)
+{
+ struct mctp_pcc_ndev *mctp_pcc_ndev;
+ struct mctp_pcc_mailbox *outbox;
+ int mctp_pcc_mtu = MCTP_MIN_MTU;
+ struct pcc_mbox_chan *pchan;
+
+ mctp_pcc_ndev = netdev_priv(ndev);
+ outbox = &mctp_pcc_ndev->outbox;
+
+ pchan = pcc_mbox_request_channel(&outbox->client, outbox->index);
+ if (IS_ERR(pchan))
+ return -1;
+
+ mctp_pcc_mtu = pchan->shmem_size;
+ pcc_mbox_free_channel(pchan);
+
+ mctp_pcc_mtu = mctp_pcc_mtu - sizeof(struct acpi_pcct_ext_pcc_shared_memory);
+ ndev->mtu = MCTP_MIN_MTU;
+ ndev->max_mtu = mctp_pcc_mtu;
+ ndev->min_mtu = MCTP_MIN_MTU;
+
+ return 0;
+}
+
+static int mctp_pcc_driver_add(struct acpi_device *acpi_dev)
+{
+ struct mctp_pcc_lookup_context context = {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;
+ 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, "FAILED to lookup PCC indexes from CRS\n");
+ return -EINVAL;
+ }
+
+ snprintf(name, sizeof(name), "mctppcc%d", context.inbox_index);
+ ndev = alloc_netdev(sizeof(*mctp_pcc_ndev), name, NET_NAME_PREDICTABLE,
+ mctp_pcc_setup);
+ if (!ndev)
+ return -ENOMEM;
+
+ mctp_pcc_ndev = netdev_priv(ndev);
+
+ mctp_pcc_ndev->inbox.index = context.inbox_index;
+ mctp_pcc_ndev->inbox.client.dev = dev;
+ mctp_pcc_ndev->outbox.index = context.outbox_index;
+ mctp_pcc_ndev->outbox.client.dev = dev;
+
+ mctp_pcc_ndev->outbox.client.tx_prepare = mctp_pcc_tx_prepare;
+ mctp_pcc_ndev->outbox.client.tx_done = mctp_pcc_tx_done;
+ mctp_pcc_ndev->acpi_device = acpi_dev;
+ mctp_pcc_ndev->ndev = ndev;
+ acpi_dev->driver_data = mctp_pcc_ndev;
+
+ rc = initialize_MTU(ndev);
+ if (rc)
+ goto free_netdev;
+
+ rc = mctp_register_netdev(ndev, NULL, MCTP_PHYS_BINDING_PCC);
+ if (rc)
+ goto free_netdev;
+
+ return devm_add_action_or_reset(dev, mctp_cleanup_netdev, ndev);
+free_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>");