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charset="utf-8" From: Adam Young 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 via ACPI by entries in DSDT/SDST and reference channels specified in the PCCT. Messages are sent on a type 3 and received on a type 4 channel. Communication with other devices use the PCC based doorbell mechanism; a shared memory segment with a corresponding interrupt and a memory register used to trigger remote interrupts. This driver takes advantage of PCC mailbox buffer management. The data section of the struct sk_buff that contains the outgoing packet is sent to the mailbox, already properly formatted as a PCC message. The driver is also reponsible for allocating a struct sk_buff that is then passed to the mailbox and used to record the data in the shared buffer. It maintains a list of both outging and incoming sk_buffs to match the data buffers with the original sk_buffs. When the Type 3 channel outbox receives a txdone response interrupt, it consumes the outgoing sk_buff, allowing it to be freed. Signed-off-by: Adam Young --- MAINTAINERS | 5 + drivers/net/mctp/Kconfig | 13 ++ drivers/net/mctp/Makefile | 1 + drivers/net/mctp/mctp-pcc.c | 347 ++++++++++++++++++++++++++++++++++++ 4 files changed, 366 insertions(+) create mode 100644 drivers/net/mctp/mctp-pcc.c diff --git a/MAINTAINERS b/MAINTAINERS index 3887d5906786..3939d816657d 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -14469,6 +14469,11 @@ F: include/net/mctpdevice.h F: include/net/netns/mctp.h F: net/mctp/ =20 +MANAGEMENT COMPONENT TRANSPORT PROTOCOL (MCTP) over PCC (MCTP-PCC) Driver +M: Adam Young +S: Maintained +F: drivers/net/mctp/mctp-pcc.c + MAPLE TREE M: Liam R. Howlett L: maple-tree@lists.infradead.org diff --git a/drivers/net/mctp/Kconfig b/drivers/net/mctp/Kconfig index cf325ab0b1ef..f69d0237f058 100644 --- a/drivers/net/mctp/Kconfig +++ b/drivers/net/mctp/Kconfig @@ -57,6 +57,19 @@ config MCTP_TRANSPORT_USB MCTP-over-USB interfaces are peer-to-peer, so each interface represents a physical connection to one remote MCTP endpoint. =20 +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 =20 endif diff --git a/drivers/net/mctp/Makefile b/drivers/net/mctp/Makefile index c36006849a1e..2276f148df7c 100644 --- a/drivers/net/mctp/Makefile +++ b/drivers/net/mctp/Makefile @@ -1,3 +1,4 @@ +obj-$(CONFIG_MCTP_TRANSPORT_PCC) +=3D mctp-pcc.o obj-$(CONFIG_MCTP_SERIAL) +=3D mctp-serial.o obj-$(CONFIG_MCTP_TRANSPORT_I2C) +=3D mctp-i2c.o obj-$(CONFIG_MCTP_TRANSPORT_I3C) +=3D 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..045711a21395 --- /dev/null +++ b/drivers/net/mctp/mctp-pcc.c @@ -0,0 +1,347 @@ +// 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 +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include +#include + +#include "../../mailbox/mailbox.h" + +#define MCTP_PAYLOAD_LENGTH 256 +#define MCTP_CMD_LENGTH 4 +#define MCTP_PCC_VERSION 0x1 /* DSP0292 a single version: 1 */ +#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; + struct sk_buff_head packets; +}; + +/* 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 net_device *ndev; + struct acpi_device *acpi_device; + struct mctp_pcc_mailbox inbox; + struct mctp_pcc_mailbox outbox; +}; + +static void *mctp_pcc_rx_alloc(struct mbox_client *c, int size) +{ + struct mctp_pcc_ndev *mctp_pcc_ndev =3D + container_of(c, struct mctp_pcc_ndev, inbox.client); + struct mctp_pcc_mailbox *box =3D &mctp_pcc_ndev->inbox; + struct sk_buff *skb; + + if (size > mctp_pcc_ndev->ndev->mtu) + return NULL; + skb =3D netdev_alloc_skb(mctp_pcc_ndev->ndev, size); + if (!skb) + return NULL; + skb_put(skb, size); + skb->protocol =3D htons(ETH_P_MCTP); + + skb_queue_head(&box->packets, skb); + + return skb->data; +} + +static void mctp_pcc_client_rx_callback(struct mbox_client *c, void *buffe= r) +{ + struct mctp_pcc_ndev *mctp_pcc_ndev; + struct pcc_header pcc_header; + struct mctp_skb_cb *cb; + struct sk_buff *skb; + + mctp_pcc_ndev =3D container_of(c, struct mctp_pcc_ndev, inbox.client); + if (!buffer) { + dev_dstats_rx_dropped(mctp_pcc_ndev->ndev); + return; + } + + skb_queue_walk(&mctp_pcc_ndev->inbox.packets, skb) { + if (skb->data !=3D buffer) + continue; + skb_unlink(skb, &mctp_pcc_ndev->inbox.packets); + 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 =3D __mctp_cb(skb); + cb->halen =3D 0; + netif_rx(skb); + return; + } + pr_warn("Unmatched packet in mctp-pcc inbox packet list"); +} + +static void mctp_pcc_tx_done(struct mbox_client *c, void *mssg, int r) +{ + struct mctp_pcc_mailbox *box; + struct sk_buff *skb; + + box =3D container_of(c, struct mctp_pcc_mailbox, client); + skb_queue_walk(&box->packets, skb) { + if (skb->data =3D=3D mssg) { + skb_unlink(skb, &box->packets); + dev_consume_skb_any(skb); + break; + } + } +} + +static netdev_tx_t mctp_pcc_tx(struct sk_buff *skb, struct net_device *nde= v) +{ + struct mctp_pcc_ndev *mpnd =3D netdev_priv(ndev); + struct pcc_header *pcc_header; + int len =3D skb->len; + int rc; + + rc =3D skb_cow_head(skb, sizeof(*pcc_header)); + if (rc) { + dev_dstats_tx_dropped(ndev); + kfree_skb(skb); + return NETDEV_TX_OK; + } + + pcc_header =3D skb_push(skb, sizeof(*pcc_header)); + pcc_header->signature =3D cpu_to_le32(PCC_SIGNATURE | mpnd->outbox.index); + pcc_header->flags =3D cpu_to_le32(PCC_CMD_COMPLETION_NOTIFY); + memcpy(&pcc_header->command, MCTP_SIGNATURE, MCTP_SIGNATURE_LENGTH); + pcc_header->length =3D cpu_to_le32(len + MCTP_SIGNATURE_LENGTH); + skb_queue_head(&mpnd->outbox.packets, skb); + + rc =3D mbox_send_message(mpnd->outbox.chan->mchan, skb->data); + + if (rc < 0) { + skb_unlink(skb, &mpnd->outbox.packets); + return NETDEV_TX_BUSY; + } + + dev_dstats_tx_add(ndev, len); + return NETDEV_TX_OK; +} + +static const struct net_device_ops mctp_pcc_netdev_ops =3D { + .ndo_start_xmit =3D mctp_pcc_tx, +}; + +static const struct mctp_netdev_ops mctp_netdev_ops =3D { + NULL +}; + +static void mctp_pcc_setup(struct net_device *ndev) +{ + ndev->type =3D ARPHRD_MCTP; + ndev->hard_header_len =3D 0; + ndev->tx_queue_len =3D 0; + ndev->flags =3D IFF_NOARP; + ndev->netdev_ops =3D &mctp_pcc_netdev_ops; + ndev->needs_free_netdev =3D true; + ndev->pcpu_stat_type =3D 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 =3D context; + struct acpi_resource_address32 *addr; + + if (ares->type !=3D PCC_DWORD_TYPE) + return AE_OK; + + addr =3D ACPI_CAST_PTR(struct acpi_resource_address32, &ares->data); + switch (luc->index) { + case 0: + luc->outbox_index =3D addr[0].address.minimum; + break; + case 1: + luc->inbox_index =3D addr[0].address.minimum; + break; + } + luc->index++; + return AE_OK; +} + +static void drain_packets(struct sk_buff_head *list) +{ + struct sk_buff *skb; + + while (!skb_queue_empty(list)) { + skb =3D skb_dequeue(list); + dev_consume_skb_any(skb); + } +} + +static void mctp_cleanup_netdev(void *data) +{ + struct mctp_pcc_ndev *mctp_pcc_ndev; + struct net_device *ndev =3D data; + + mctp_pcc_ndev =3D netdev_priv(ndev); + drain_packets(&mctp_pcc_ndev->outbox.packets); + drain_packets(&mctp_pcc_ndev->inbox.packets); + + mctp_unregister_netdev(ndev); +} + +static void mctp_cleanup_channel(void *data) +{ + struct pcc_mbox_chan *chan =3D data; + + pcc_mbox_free_channel(chan); +} + +static int mctp_pcc_initialize_mailbox(struct device *dev, + struct mctp_pcc_mailbox *box, u32 index) +{ + box->index =3D index; + skb_queue_head_init(&box->packets); + box->chan =3D pcc_mbox_request_channel(&box->client, index); + + box->client.dev =3D dev; + if (IS_ERR(box->chan)) + return PTR_ERR(box->chan); + return devm_add_action_or_reset(dev, mctp_cleanup_channel, box->chan); +} + +static int mctp_pcc_driver_add(struct acpi_device *acpi_dev) +{ + struct mctp_pcc_lookup_context context =3D {0}; + struct mctp_pcc_ndev *mctp_pcc_ndev; + struct device *dev =3D &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 =3D acpi_device_handle(acpi_dev); + status =3D 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; + } + + snprintf(name, sizeof(name), "mctpipcc%d", context.inbox_index); + ndev =3D alloc_netdev(sizeof(*mctp_pcc_ndev), name, NET_NAME_PREDICTABLE, + mctp_pcc_setup); + if (!ndev) + return -ENOMEM; + + mctp_pcc_ndev =3D netdev_priv(ndev); + spin_lock_init(&mctp_pcc_ndev->lock); + + /* inbox initialization */ + rc =3D mctp_pcc_initialize_mailbox(dev, &mctp_pcc_ndev->inbox, + context.inbox_index); + if (rc) + goto free_netdev; + + mctp_pcc_ndev->inbox.chan->rx_alloc =3D mctp_pcc_rx_alloc; + mctp_pcc_ndev->inbox.client.rx_callback =3D mctp_pcc_client_rx_callback; + + /* outbox initialization */ + rc =3D mctp_pcc_initialize_mailbox(dev, &mctp_pcc_ndev->outbox, + context.outbox_index); + if (rc) + goto free_netdev; + + mctp_pcc_ndev->outbox.chan->manage_writes =3D true; + mctp_pcc_ndev->outbox.client.tx_done =3D mctp_pcc_tx_done; + mctp_pcc_ndev->acpi_device =3D acpi_dev; + mctp_pcc_ndev->ndev =3D ndev; + acpi_dev->driver_data =3D 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 =3D mctp_pcc_ndev->outbox.chan->shmem_size - + sizeof(struct pcc_header); + ndev->mtu =3D MCTP_MIN_MTU; + ndev->max_mtu =3D mctp_pcc_mtu; + ndev->min_mtu =3D 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 =3D mctp_register_netdev(ndev, &mctp_netdev_ops, 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[] =3D { + { "DMT0001" }, + {} +}; + +static struct acpi_driver mctp_pcc_driver =3D { + .name =3D "mctp_pcc", + .class =3D "Unknown", + .ids =3D mctp_pcc_device_ids, + .ops =3D { + .add =3D 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 "); --=20 2.43.0