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From: admiyo@os.amperecomputing.com
To: Jeremy Kerr <jk@codeconstruct.com.au>,
	Matt Johnston <matt@codeconstruct.com.au>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>
Cc: netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Adam Young <admiyo@os.amperecomputing.com>
Subject: [PATCH 1/3] mctp pcc: Implement MCTP over PCC Transport
Date: Mon, 13 May 2024 13:35:44 -0400
Message-Id: <20240513173546.679061-2-admiyo@os.amperecomputing.com>
In-Reply-To: <20240513173546.679061-1-admiyo@os.amperecomputing.com>
References: <20240513173546.679061-1-admiyo@os.amperecomputing.com>
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From: Adam Young <admiyo@os.amperecomputing.com>

Implementation of DMTF DSP:0292
Management Control Transport Protocol(MCTP)  over
Platform Communication Channel(PCC)

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    |  12 ++
 drivers/net/mctp/Makefile   |   1 +
 drivers/net/mctp/mctp-pcc.c | 368 ++++++++++++++++++++++++++++++++++++
 3 files changed, 381 insertions(+)
 create mode 100644 drivers/net/mctp/mctp-pcc.c

diff --git a/drivers/net/mctp/Kconfig b/drivers/net/mctp/Kconfig
index ce9d2d2ccf3b..16bad87c9a6f 100644
--- a/drivers/net/mctp/Kconfig
+++ b/drivers/net/mctp/Kconfig
@@ -42,6 +42,18 @@ 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 MCTP_FLOWS
+	help
+	  Provides a driver to access MCTP devices over PCC transport,
+	  A MCTP protocol network device is created for each entry int the DST/SDST
+	  that matches the identifier.  The PCC 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..7242eedd2759
--- /dev/null
+++ b/drivers/net/mctp/mctp-pcc.c
@@ -0,0 +1,368 @@
+// 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>
+#include <net/pkt_sched.h>
+
+#define SPDM_VERSION_OFFSET 1
+#define SPDM_REQ_RESP_OFFSET 2
+#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
+
+struct mctp_pcc_hdr {
+	u32 signature;
+	u32  flags;
+	u32 length;
+	char mctp_signature[4];
+};
+
+struct mctp_pcc_packet {
+	struct mctp_pcc_hdr pcc_header;
+	union {
+		struct mctp_hdr     mctp_header;
+		unsigned char header_data[sizeof(struct mctp_hdr)];
+	};
+	unsigned char payload[MCTP_PAYLOAD_LENGTH];
+};
+
+struct mctp_pcc_hw_addr {
+	int inbox_index;
+	int outbox_index;
+};
+
+/* The netdev structure. One of these per PCC adapter. */
+struct mctp_pcc_ndev {
+	struct list_head head;
+	/* spinlock to serialize access from netdev to pcc buffer*/
+	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;
+	void (*cleanup_channel)(struct pcc_mbox_chan *in_chan);
+};
+
+static struct list_head mctp_pcc_ndevs;
+
+static struct mctp_pcc_packet *mctp_pcc_extract_data(struct sk_buff *old_skb,
+						     void *buffer, int outbox_index)
+{
+	struct mctp_pcc_packet *mpp;
+
+	mpp = buffer;
+	writel(PCC_MAGIC | outbox_index, &mpp->pcc_header.signature);
+	writel(0x1, &mpp->pcc_header.flags);
+	memcpy_toio(mpp->pcc_header.mctp_signature, MCTP_SIGNATURE, SIGNATURE_LENGTH);
+	writel(old_skb->len + SIGNATURE_LENGTH,  &mpp->pcc_header.length);
+	memcpy_toio(mpp->header_data,    old_skb->data, old_skb->len);
+	return mpp;
+}
+
+static void mctp_pcc_client_rx_callback(struct mbox_client *c, void *)
+{
+	struct sk_buff *skb;
+	struct mctp_pcc_packet *mpp;
+	struct mctp_skb_cb *cb;
+	int data_len;
+	unsigned long buf_ptr_val;
+	struct mctp_pcc_ndev *mctp_pcc_dev = container_of(c, struct mctp_pcc_ndev, inbox_client);
+	void *skb_buf;
+
+	mpp = (struct mctp_pcc_packet *)mctp_pcc_dev->pcc_comm_inbox_addr;
+	buf_ptr_val = (unsigned long)mpp;
+	data_len = readl(&mpp->pcc_header.length) + MCTP_HEADER_LENGTH;
+	skb = netdev_alloc_skb(mctp_pcc_dev->mdev.dev, data_len);
+	if (!skb) {
+		mctp_pcc_dev->mdev.dev->stats.rx_dropped++;
+		return;
+	}
+	skb->protocol = htons(ETH_P_MCTP);
+	skb_buf = skb_put(skb, data_len);
+	memcpy_fromio(skb_buf, mpp, 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;
+	skb->dev =  mctp_pcc_dev->mdev.dev;
+	netif_rx(skb);
+}
+
+static netdev_tx_t mctp_pcc_tx(struct sk_buff *skb, struct net_device *ndev)
+{
+	unsigned char *buffer;
+	struct mctp_pcc_ndev *mpnd;
+	struct mctp_pcc_packet  *mpp;
+	unsigned long flags;
+	int rc;
+
+	netif_stop_queue(ndev);
+	ndev->stats.tx_bytes += skb->len;
+	mpnd = (struct mctp_pcc_ndev *)netdev_priv(ndev);
+	spin_lock_irqsave(&mpnd->lock, flags);
+	buffer =  mpnd->pcc_comm_outbox_addr;
+	mpp = mctp_pcc_extract_data(skb, mpnd->pcc_comm_outbox_addr, mpnd->hw_addr.outbox_index);
+	rc = mpnd->out_chan->mchan->mbox->ops->send_data(mpnd->out_chan->mchan, mpp);
+	spin_unlock_irqrestore(&mpnd->lock, flags);
+
+	dev_consume_skb_any(skb);
+	netif_start_queue(ndev);
+	if (!rc)
+		return NETDEV_TX_OK;
+	return NETDEV_TX_BUSY;
+}
+
+static const struct net_device_ops mctp_pcc_netdev_ops = {
+	.ndo_start_xmit = mctp_pcc_tx,
+	.ndo_uninit = NULL
+};
+
+static void  mctp_pcc_setup(struct net_device *ndev)
+{
+	ndev->type = ARPHRD_MCTP;
+	ndev->hard_header_len = 0;
+	ndev->addr_len = sizeof(struct mctp_pcc_hw_addr);
+	ndev->tx_queue_len = DEFAULT_TX_QUEUE_LEN;
+	ndev->flags = IFF_NOARP;
+	ndev->netdev_ops = &mctp_pcc_netdev_ops;
+	ndev->needs_free_netdev = true;
+}
+
+static int create_mctp_pcc_netdev(struct acpi_device *acpi_dev,
+				  struct device *dev, int inbox_index,
+				  int outbox_index)
+{
+	int rc;
+	int mctp_pcc_mtu;
+	char name[32];
+	struct net_device *ndev;
+	struct mctp_pcc_ndev *mctp_pcc_dev;
+	struct mctp_pcc_hw_addr physical_link_addr;
+
+	snprintf(name, sizeof(name), "mctpipcc%x", inbox_index);
+	ndev = alloc_netdev(sizeof(struct mctp_pcc_ndev), name, NET_NAME_ENUM, mctp_pcc_setup);
+	if (!ndev)
+		return -ENOMEM;
+	mctp_pcc_dev = (struct mctp_pcc_ndev *)netdev_priv(ndev);
+	INIT_LIST_HEAD(&mctp_pcc_dev->head);
+	spin_lock_init(&mctp_pcc_dev->lock);
+
+	mctp_pcc_dev->outbox_client.tx_prepare = NULL;
+	mctp_pcc_dev->outbox_client.tx_done = NULL;
+	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->cleanup_channel = pcc_mbox_free_channel;
+	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;
+
+/* 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_pcc_mtu;
+	ndev->max_mtu = mctp_pcc_mtu;
+	ndev->min_mtu = MCTP_MIN_MTU;
+
+	physical_link_addr.inbox_index =
+		htonl(mctp_pcc_dev->hw_addr.inbox_index);
+	physical_link_addr.outbox_index =
+		htonl(mctp_pcc_dev->hw_addr.outbox_index);
+	dev_addr_set(ndev, (const u8 *)&physical_link_addr);
+	rc = register_netdev(ndev);
+	if (rc)
+		goto cleanup_in_channel;
+	list_add_tail(&mctp_pcc_dev->head, &mctp_pcc_ndevs);
+	return 0;
+cleanup_in_channel:
+	mctp_pcc_dev->cleanup_channel(mctp_pcc_dev->in_chan);
+cleanup_out_channel:
+	mctp_pcc_dev->cleanup_channel(mctp_pcc_dev->out_chan);
+free_netdev:
+	unregister_netdev(ndev);
+	free_netdev(ndev);
+	return rc;
+}
+
+struct lookup_context {
+	int index;
+	int inbox_index;
+	int 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 0x0c:
+	case 0x0a:
+		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 *adev)
+{
+	int inbox_index;
+	int outbox_index;
+	acpi_handle dev_handle;
+	acpi_status status;
+	struct lookup_context context = {0, 0, 0};
+
+	dev_info(&adev->dev, "Adding mctp_pcc device for HID  %s\n", acpi_device_hid(adev));
+	dev_handle = acpi_device_handle(adev);
+	status = acpi_walk_resources(dev_handle, "_CRS", lookup_pcct_indices, &context);
+	if (ACPI_SUCCESS(status)) {
+		inbox_index = context.inbox_index;
+		outbox_index = context.outbox_index;
+		return create_mctp_pcc_netdev(adev, &adev->dev, inbox_index, outbox_index);
+	}
+	dev_err(&adev->dev, "FAILURE to lookup PCC indexes from CRS");
+	return -EINVAL;
+};
+
+/* pass in adev=NULL to remove all devices
+ */
+static void mctp_pcc_driver_remove(struct acpi_device *adev)
+{
+	struct mctp_pcc_ndev *mctp_pcc_dev = NULL;
+	struct list_head *ptr;
+	struct list_head *tmp;
+
+	list_for_each_safe(ptr, tmp, &mctp_pcc_ndevs) {
+		mctp_pcc_dev = list_entry(ptr, struct mctp_pcc_ndev, head);
+		if (!adev || mctp_pcc_dev->acpi_device == adev) {
+			struct net_device *ndev;
+
+			mctp_pcc_dev->cleanup_channel(mctp_pcc_dev->out_chan);
+			mctp_pcc_dev->cleanup_channel(mctp_pcc_dev->in_chan);
+			ndev = mctp_pcc_dev->mdev.dev;
+			if (ndev)
+				mctp_unregister_netdev(ndev);
+			list_del(ptr);
+			if (adev)
+				break;
+		}
+	}
+};
+
+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,
+		.notify = NULL,
+	},
+	.owner = THIS_MODULE,
+
+};
+
+static int __init mctp_pcc_mod_init(void)
+{
+	int rc;
+
+	pr_info("initializing MCTP over PCC\n");
+	INIT_LIST_HEAD(&mctp_pcc_ndevs);
+	rc = acpi_bus_register_driver(&mctp_pcc_driver);
+	if (rc < 0)
+		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Error registering driver\n"));
+	return rc;
+}
+
+static __exit void mctp_pcc_mod_exit(void)
+{
+	pr_info("Removing MCTP over PCC transport driver\n");
+	mctp_pcc_driver_remove(NULL);
+	acpi_bus_unregister_driver(&mctp_pcc_driver);
+}
+
+module_init(mctp_pcc_mod_init);
+module_exit(mctp_pcc_mod_exit);
+
+MODULE_DEVICE_TABLE(acpi, mctp_pcc_device_ids);
+
+MODULE_DESCRIPTION("MCTP PCC device");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Adam Young <admiyo@os.amperecomputing.com>");
-- 
2.34.1