[PATCH v5 3/3] mctp pcc: Implement MCTP over PCC Transport

[admiyo]

From: Adam Young <admiyo@xxxxxxxxxxxxxxxxxxxxxx>

Implementation of network driver for
Management Control Transport Protocol(MCTP) over
Platform Communication Channel(PCC)

DMTF DSP:0292

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@xxxxxxxxxxxxxxxxxxxxxx>
---
 drivers/net/mctp/Kconfig    |  13 ++
 drivers/net/mctp/Makefile   |   1 +
 drivers/net/mctp/mctp-pcc.c | 325 ++++++++++++++++++++++++++++++++++++
 3 files changed, 339 insertions(+)
 create mode 100644 drivers/net/mctp/mctp-pcc.c

diff --git a/drivers/net/mctp/Kconfig b/drivers/net/mctp/Kconfig
index ce9d2d2ccf3b..9958b162af65 100644
--- a/drivers/net/mctp/Kconfig
+++ b/drivers/net/mctp/Kconfig
@@ -42,6 +42,19 @@ 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"
+	select 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
+	  commuinucation 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..055d6408e1d7
--- /dev/null
+++ b/drivers/net/mctp/mctp-pcc.c
@@ -0,0 +1,325 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * mctp-pcc.c - Driver for MCTP over PCC.
+ * Copyright (c) 2024, Ampere Computing LLC
+ */
+
+#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 SIGNATURE_LENGTH	4
+#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
+#define PCC_ACK_FLAG_MASK	0x1
+
+struct mctp_pcc_hdr {
+	u32 signature;
+	u32 flags;
+	u32 length;
+	char mctp_signature[4];
+};
+
+struct mctp_pcc_hw_addr {
+	u32 inbox_index;
+	u32 outbox_index;
+};
+
+/* 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 pcc_mbox_chan *in_chan;
+	struct pcc_mbox_chan *out_chan;
+	struct mbox_client outbox_client;
+	struct mbox_client inbox_client;
+	void __iomem *pcc_comm_inbox_addr;
+	void __iomem *pcc_comm_outbox_addr;
+	struct mctp_pcc_hw_addr hw_addr;
+};
+
+static void mctp_pcc_client_rx_callback(struct mbox_client *c, void *buffer)
+{
+	struct mctp_pcc_ndev *mctp_pcc_dev;
+	struct mctp_pcc_hdr mctp_pcc_hdr;
+	struct mctp_skb_cb *cb;
+	struct sk_buff *skb;
+	void *skb_buf;
+	u32 data_len;
+
+	mctp_pcc_dev = container_of(c, struct mctp_pcc_ndev, inbox_client);
+	memcpy_fromio(&mctp_pcc_hdr, mctp_pcc_dev->pcc_comm_inbox_addr,
+		      sizeof(struct mctp_pcc_hdr));
+	data_len = mctp_pcc_hdr.length + MCTP_HEADER_LENGTH;
+
+	if (data_len > mctp_pcc_dev->mdev.dev->mtu) {
+		mctp_pcc_dev->mdev.dev->stats.rx_dropped++;
+		return;
+	}
+
+	skb = netdev_alloc_skb(mctp_pcc_dev->mdev.dev, data_len);
+	if (!skb) {
+		mctp_pcc_dev->mdev.dev->stats.rx_dropped++;
+		return;
+	}
+	mctp_pcc_dev->mdev.dev->stats.rx_packets++;
+	mctp_pcc_dev->mdev.dev->stats.rx_bytes += data_len;
+	skb->protocol = htons(ETH_P_MCTP);
+	skb_buf = skb_put(skb, data_len);
+	memcpy_fromio(skb_buf, mctp_pcc_dev->pcc_comm_inbox_addr, 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_hdr pcc_header;
+	struct mctp_pcc_ndev *mpnd;
+	void __iomem *buffer;
+	unsigned long flags;
+
+	ndev->stats.tx_bytes += skb->len;
+	ndev->stats.tx_packets++;
+	mpnd = netdev_priv(ndev);
+
+	spin_lock_irqsave(&mpnd->lock, flags);
+	buffer = mpnd->pcc_comm_outbox_addr;
+	pcc_header.signature = PCC_MAGIC | mpnd->hw_addr.outbox_index;
+	pcc_header.flags = PCC_HEADER_FLAGS;
+	memcpy(pcc_header.mctp_signature, MCTP_SIGNATURE, SIGNATURE_LENGTH);
+	pcc_header.length = skb->len + SIGNATURE_LENGTH;
+	memcpy_toio(buffer, &pcc_header, sizeof(struct mctp_pcc_hdr));
+	memcpy_toio(buffer + sizeof(struct mctp_pcc_hdr), skb->data, skb->len);
+	mpnd->out_chan->mchan->mbox->ops->send_data(mpnd->out_chan->mchan,
+						    NULL);
+	spin_unlock_irqrestore(&mpnd->lock, flags);
+
+	dev_consume_skb_any(skb);
+	return NETDEV_TX_OK;
+}
+
+static void
+mctp_pcc_net_stats(struct net_device *net_dev,
+		   struct rtnl_link_stats64 *stats)
+{
+	stats->rx_errors = 0;
+	stats->rx_packets = net_dev->stats.rx_packets;
+	stats->tx_packets = net_dev->stats.tx_packets;
+	stats->rx_dropped = 0;
+	stats->tx_bytes = net_dev->stats.tx_bytes;
+	stats->rx_bytes = net_dev->stats.rx_bytes;
+}
+
+static const struct net_device_ops mctp_pcc_netdev_ops = {
+	.ndo_start_xmit = mctp_pcc_tx,
+	.ndo_get_stats64 = mctp_pcc_net_stats,
+};
+
+static void  mctp_pcc_setup(struct net_device *ndev)
+{
+	ndev->type = ARPHRD_MCTP;
+	ndev->hard_header_len = 0;
+	ndev->addr_len = 0;
+	ndev->tx_queue_len = 0;
+	ndev->flags = IFF_NOARP;
+	ndev->netdev_ops = &mctp_pcc_netdev_ops;
+	ndev->needs_free_netdev = true;
+}
+
+struct lookup_context {
+	int index;
+	u32 inbox_index;
+	u32 outbox_index;
+};
+
+static acpi_status lookup_pcct_indices(struct acpi_resource *ares,
+				       void *context)
+{
+	struct acpi_resource_address32 *addr;
+	struct lookup_context *luc = context;
+
+	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 int mctp_pcc_driver_add(struct acpi_device *acpi_dev)
+{
+	struct lookup_context context = {0, 0, 0};
+	struct mctp_pcc_ndev *mctp_pcc_dev;
+	struct net_device *ndev;
+	acpi_handle dev_handle;
+	acpi_status status;
+	struct device *dev;
+	int mctp_pcc_mtu;
+	int outbox_index;
+	int inbox_index;
+	char name[32];
+	int rc;
+
+	dev_dbg(&acpi_dev->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(&acpi_dev->dev, "FAILURE to lookup PCC indexes from CRS");
+		return -EINVAL;
+	}
+	inbox_index = context.inbox_index;
+	outbox_index = context.outbox_index;
+	dev = &acpi_dev->dev;
+
+	snprintf(name, sizeof(name), "mctpipcc%d", inbox_index);
+	ndev = alloc_netdev(sizeof(struct mctp_pcc_ndev), name, NET_NAME_ENUM,
+			    mctp_pcc_setup);
+	if (!ndev)
+		return -ENOMEM;
+	mctp_pcc_dev = netdev_priv(ndev);
+	spin_lock_init(&mctp_pcc_dev->lock);
+
+	mctp_pcc_dev->hw_addr.inbox_index = inbox_index;
+	mctp_pcc_dev->hw_addr.outbox_index = outbox_index;
+	mctp_pcc_dev->inbox_client.rx_callback = mctp_pcc_client_rx_callback;
+	mctp_pcc_dev->out_chan =
+		pcc_mbox_request_channel(&mctp_pcc_dev->outbox_client,
+					 outbox_index);
+	if (IS_ERR(mctp_pcc_dev->out_chan)) {
+		rc = PTR_ERR(mctp_pcc_dev->out_chan);
+		goto free_netdev;
+	}
+	mctp_pcc_dev->in_chan =
+		pcc_mbox_request_channel(&mctp_pcc_dev->inbox_client,
+					 inbox_index);
+	if (IS_ERR(mctp_pcc_dev->in_chan)) {
+		rc = PTR_ERR(mctp_pcc_dev->in_chan);
+		goto cleanup_out_channel;
+	}
+	mctp_pcc_dev->pcc_comm_inbox_addr =
+		devm_ioremap(dev, mctp_pcc_dev->in_chan->shmem_base_addr,
+			     mctp_pcc_dev->in_chan->shmem_size);
+	if (!mctp_pcc_dev->pcc_comm_inbox_addr) {
+		rc = -EINVAL;
+		goto cleanup_in_channel;
+	}
+	mctp_pcc_dev->pcc_comm_outbox_addr =
+		devm_ioremap(dev, mctp_pcc_dev->out_chan->shmem_base_addr,
+			     mctp_pcc_dev->out_chan->shmem_size);
+	if (!mctp_pcc_dev->pcc_comm_outbox_addr) {
+		rc = -EINVAL;
+		goto cleanup_in_channel;
+	}
+	mctp_pcc_dev->acpi_device = acpi_dev;
+	mctp_pcc_dev->inbox_client.dev = dev;
+	mctp_pcc_dev->outbox_client.dev = dev;
+	mctp_pcc_dev->mdev.dev = ndev;
+	acpi_dev->driver_data = mctp_pcc_dev;
+
+	/* 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_dev->out_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;
+
+	rc = register_netdev(ndev);
+	if (rc)
+		goto cleanup_in_channel;
+	return 0;
+
+cleanup_in_channel:
+	pcc_mbox_free_channel(mctp_pcc_dev->in_chan);
+cleanup_out_channel:
+	pcc_mbox_free_channel(mctp_pcc_dev->out_chan);
+free_netdev:
+	unregister_netdev(ndev);
+	free_netdev(ndev);
+	return rc;
+}
+
+static void mctp_pcc_driver_remove(struct acpi_device *adev)
+{
+	struct mctp_pcc_ndev *mctp_pcc_ndev = acpi_driver_data(adev);
+
+	pcc_mbox_free_channel(mctp_pcc_ndev->out_chan);
+	pcc_mbox_free_channel(mctp_pcc_ndev->in_chan);
+	mctp_unregister_netdev(mctp_pcc_ndev->mdev.dev);
+}
+
+static const struct acpi_device_id mctp_pcc_device_ids[] = {
+	{ "DMT0001", 0},
+	{ "", 0},
+};
+
+static struct acpi_driver mctp_pcc_driver = {
+	.name = "mctp_pcc",
+	.class = "Unknown",
+	.ids = mctp_pcc_device_ids,
+	.ops = {
+		.add = mctp_pcc_driver_add,
+		.remove = mctp_pcc_driver_remove,
+	},
+};
+
+module_acpi_driver(mctp_pcc_driver);
+
+MODULE_DEVICE_TABLE(acpi, mctp_pcc_device_ids);
+
+MODULE_DESCRIPTION("MCTP PCC device");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Adam Young <admiyo@xxxxxxxxxxxxxxxxxxxxxx>");
-- 
2.34.1