Message-ID: <dbadafab-c70c-490f-bd34-ac7c1026cda8@amperemail.onmicrosoft.com>
Date: Wed, 15 Jan 2025 11:21:19 -0500
From: Adam Young <admiyo@...eremail.onmicrosoft.com>
To: admiyo@...amperecomputing.com, Jeremy Kerr <jk@...econstruct.com.au>,
 Matt Johnston <matt@...econstruct.com.au>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Sudeep Holla <sudeep.holla@....com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Huisong Li <lihuisong@...wei.com>
Subject: Re: [PATCH v14 1/1] mctp pcc: Implement MCTP over PCC Transport

Let me self report the tab issue on the maintainers file.  My editor 
originally put in spaces.

I made the change in code and did not update  the patch, so it fails 
checkpatch.  Update in next version.




On 1/14/25 14:31, admiyo@...amperecomputing.com wrote:
> From: Adam Young <admiyo@...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 via ACPI 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@...amperecomputing.com>
> ---
>   MAINTAINERS                 |   6 +
>   drivers/net/mctp/Kconfig    |  13 ++
>   drivers/net/mctp/Makefile   |   1 +
>   drivers/net/mctp/mctp-pcc.c | 313 ++++++++++++++++++++++++++++++++++++
>   4 files changed, 333 insertions(+)
>   create mode 100644 drivers/net/mctp/mctp-pcc.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 1579124ef426..a4b8168cb346 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -13789,6 +13789,12 @@ F:	include/net/mctpdevice.h
>   F:	include/net/netns/mctp.h
>   F:	net/mctp/
>   
> +MANAGEMENT COMPONENT TRANSPORT PROTOCOL (MCTP) over PCC (MCTP-PCC) Driver
> +M:      Adam Young <admiyo@...amperecomputing.com>
> +L:      netdev@...r.kernel.org
> +S:      Maintained
> +F:      drivers/net/mctp/mctp-pcc.c
> +
>   MAPLE TREE
>   M:	Liam R. Howlett <Liam.Howlett@...cle.com>
>   L:	maple-tree@...ts.infradead.org
> 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..87283e5b1490
> --- /dev/null
> +++ b/drivers/net/mctp/mctp-pcc.c
> @@ -0,0 +1,313 @@
> +// 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 {
> +	__le32 signature;
> +	__le32 flags;
> +	__le32 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 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 = le32_to_cpu(mctp_pcc_hdr.length) + MCTP_HEADER_LENGTH;
> +	if (data_len > mctp_pcc_ndev->mdev.dev->mtu) {
> +		dev_dstats_rx_dropped(mctp_pcc_ndev->mdev.dev);
> +		return;
> +	}
> +
> +	skb = netdev_alloc_skb(mctp_pcc_ndev->mdev.dev, data_len);
> +	if (!skb) {
> +		dev_dstats_rx_dropped(mctp_pcc_ndev->mdev.dev);
> +		return;
> +	}
> +	dev_dstats_rx_add(mctp_pcc_ndev->mdev.dev, data_len);
> +
> +	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;
> +	void __iomem *buffer;
> +	unsigned long flags;
> +	int len = skb->len;
> +
> +	dev_dstats_tx_add(ndev, len);
> +
> +	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 = cpu_to_le32(PCC_MAGIC | mpnd->outbox.index);
> +	mctp_pcc_header->flags = cpu_to_le32(PCC_HEADER_FLAGS);
> +	memcpy(mctp_pcc_header->mctp_signature, MCTP_SIGNATURE,
> +	       MCTP_SIGNATURE_LENGTH);
> +	mctp_pcc_header->length = cpu_to_le32(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 const struct mctp_netdev_ops mctp_netdev_ops = {
> +	NULL
> +};
> +
> +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);
> +	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 = mctp_register_netdev(ndev, &mctp_netdev_ops, MCTP_PHYS_BINDING_PCC);
> +	if (rc)
> +		goto cleanup_netdev;
> +	rc = devm_add_action_or_reset(dev, mctp_cleanup_netdev, ndev);
> +	if (rc)
> +		goto cleanup_netdev;
> +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@...amperecomputing.com>");

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