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// SPDX-License-Identifier: GPL-2.0
/*
* System Control and Management Interface (SCMI) Message Mailbox Transport
* driver.
*
* Copyright (C) 2019-2024 ARM Ltd.
*/
#include <linux/err.h>
#include <linux/device.h>
#include <linux/mailbox_client.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include "../common.h"
/**
* struct scmi_mailbox - Structure representing a SCMI mailbox transport
*
* @cl: Mailbox Client
* @chan: Transmit/Receive mailbox uni/bi-directional channel
* @chan_receiver: Optional Receiver mailbox unidirectional channel
* @chan_platform_receiver: Optional Platform Receiver mailbox unidirectional channel
* @cinfo: SCMI channel info
* @shmem: Transmit/Receive shared memory area
* @chan_lock: Lock that prevents multiple xfers from being queued
*/
struct scmi_mailbox {
struct mbox_client cl;
struct mbox_chan *chan;
struct mbox_chan *chan_receiver;
struct mbox_chan *chan_platform_receiver;
struct scmi_chan_info *cinfo;
struct scmi_shared_mem __iomem *shmem;
struct mutex chan_lock;
};
#define client_to_scmi_mailbox(c) container_of(c, struct scmi_mailbox, cl)
static struct scmi_transport_core_operations *core;
static void tx_prepare(struct mbox_client *cl, void *m)
{
struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
core->shmem->tx_prepare(smbox->shmem, m, smbox->cinfo);
}
static void rx_callback(struct mbox_client *cl, void *m)
{
struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
/*
* An A2P IRQ is NOT valid when received while the platform still has
* the ownership of the channel, because the platform at first releases
* the SMT channel and then sends the completion interrupt.
*
* This addresses a possible race condition in which a spurious IRQ from
* a previous timed-out reply which arrived late could be wrongly
* associated with the next pending transaction.
*/
if (cl->knows_txdone &&
!core->shmem->channel_free(smbox->shmem)) {
dev_warn(smbox->cinfo->dev, "Ignoring spurious A2P IRQ !\n");
core->bad_message_trace(smbox->cinfo,
core->shmem->read_header(smbox->shmem),
MSG_MBOX_SPURIOUS);
return;
}
core->rx_callback(smbox->cinfo,
core->shmem->read_header(smbox->shmem), NULL);
}
static bool mailbox_chan_available(struct device_node *of_node, int idx)
{
int num_mb;
/*
* Just check if bidirrectional channels are involved, and check the
* index accordingly; proper full validation will be made later
* in mailbox_chan_setup().
*/
num_mb = of_count_phandle_with_args(of_node, "mboxes", "#mbox-cells");
if (num_mb == 3 && idx == 1)
idx = 2;
return !of_parse_phandle_with_args(of_node, "mboxes",
"#mbox-cells", idx, NULL);
}
/**
* mailbox_chan_validate - Validate transport configuration and map channels
*
* @cdev: Reference to the underlying transport device carrying the
* of_node descriptor to analyze.
* @a2p_rx_chan: A reference to an optional unidirectional channel to use
* for replies on the a2p channel. Set as zero if not present.
* @p2a_chan: A reference to the optional p2a channel.
* Set as zero if not present.
* @p2a_rx_chan: A reference to the optional p2a completion channel.
* Set as zero if not present.
*
* At first, validate the transport configuration as described in terms of
* 'mboxes' and 'shmem', then determin which mailbox channel indexes are
* appropriate to be use in the current configuration.
*
* Return: 0 on Success or error
*/
static int mailbox_chan_validate(struct device *cdev, int *a2p_rx_chan,
int *p2a_chan, int *p2a_rx_chan)
{
int num_mb, num_sh, ret = 0;
struct device_node *np = cdev->of_node;
num_mb = of_count_phandle_with_args(np, "mboxes", "#mbox-cells");
num_sh = of_count_phandle_with_args(np, "shmem", NULL);
dev_dbg(cdev, "Found %d mboxes and %d shmems !\n", num_mb, num_sh);
/* Bail out if mboxes and shmem descriptors are inconsistent */
if (num_mb <= 0 || num_sh <= 0 || num_sh > 2 || num_mb > 4 ||
(num_mb == 1 && num_sh != 1) || (num_mb == 3 && num_sh != 2) ||
(num_mb == 4 && num_sh != 2)) {
dev_warn(cdev,
"Invalid channel descriptor for '%s' - mbs:%d shm:%d\n",
of_node_full_name(np), num_mb, num_sh);
return -EINVAL;
}
/* Bail out if provided shmem descriptors do not refer distinct areas */
if (num_sh > 1) {
struct device_node *np_tx __free(device_node) =
of_parse_phandle(np, "shmem", 0);
struct device_node *np_rx __free(device_node) =
of_parse_phandle(np, "shmem", 1);
if (!np_tx || !np_rx || np_tx == np_rx) {
dev_warn(cdev, "Invalid shmem descriptor for '%s'\n",
of_node_full_name(np));
ret = -EINVAL;
}
}
/* Calculate channels IDs to use depending on mboxes/shmem layout */
if (!ret) {
switch (num_mb) {
case 1:
*a2p_rx_chan = 0;
*p2a_chan = 0;
*p2a_rx_chan = 0;
break;
case 2:
if (num_sh == 2) {
*a2p_rx_chan = 0;
*p2a_chan = 1;
} else {
*a2p_rx_chan = 1;
*p2a_chan = 0;
}
*p2a_rx_chan = 0;
break;
case 3:
*a2p_rx_chan = 1;
*p2a_chan = 2;
*p2a_rx_chan = 0;
break;
case 4:
*a2p_rx_chan = 1;
*p2a_chan = 2;
*p2a_rx_chan = 3;
break;
}
}
return ret;
}
static int mailbox_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
bool tx)
{
const char *desc = tx ? "Tx" : "Rx";
struct device *cdev = cinfo->dev;
struct scmi_mailbox *smbox;
int ret, a2p_rx_chan, p2a_chan, p2a_rx_chan;
struct mbox_client *cl;
ret = mailbox_chan_validate(cdev, &a2p_rx_chan, &p2a_chan, &p2a_rx_chan);
if (ret)
return ret;
if (!tx && !p2a_chan)
return -ENODEV;
smbox = devm_kzalloc(dev, sizeof(*smbox), GFP_KERNEL);
if (!smbox)
return -ENOMEM;
smbox->shmem = core->shmem->setup_iomap(cinfo, dev, tx, NULL);
if (IS_ERR(smbox->shmem))
return PTR_ERR(smbox->shmem);
cl = &smbox->cl;
cl->dev = cdev;
cl->tx_prepare = tx ? tx_prepare : NULL;
cl->rx_callback = rx_callback;
cl->tx_block = false;
cl->knows_txdone = tx;
smbox->chan = mbox_request_channel(cl, tx ? 0 : p2a_chan);
if (IS_ERR(smbox->chan)) {
ret = PTR_ERR(smbox->chan);
if (ret != -EPROBE_DEFER)
dev_err(cdev,
"failed to request SCMI %s mailbox\n", desc);
return ret;
}
/* Additional unidirectional channel for TX if needed */
if (tx && a2p_rx_chan) {
smbox->chan_receiver = mbox_request_channel(cl, a2p_rx_chan);
if (IS_ERR(smbox->chan_receiver)) {
ret = PTR_ERR(smbox->chan_receiver);
if (ret != -EPROBE_DEFER)
dev_err(cdev, "failed to request SCMI Tx Receiver mailbox\n");
return ret;
}
}
if (!tx && p2a_rx_chan) {
smbox->chan_platform_receiver = mbox_request_channel(cl, p2a_rx_chan);
if (IS_ERR(smbox->chan_platform_receiver)) {
ret = PTR_ERR(smbox->chan_platform_receiver);
if (ret != -EPROBE_DEFER)
dev_err(cdev, "failed to request SCMI P2A Receiver mailbox\n");
return ret;
}
}
cinfo->transport_info = smbox;
smbox->cinfo = cinfo;
mutex_init(&smbox->chan_lock);
return 0;
}
static int mailbox_chan_free(int id, void *p, void *data)
{
struct scmi_chan_info *cinfo = p;
struct scmi_mailbox *smbox = cinfo->transport_info;
if (smbox && !IS_ERR(smbox->chan)) {
mbox_free_channel(smbox->chan);
mbox_free_channel(smbox->chan_receiver);
mbox_free_channel(smbox->chan_platform_receiver);
cinfo->transport_info = NULL;
smbox->chan = NULL;
smbox->chan_receiver = NULL;
smbox->chan_platform_receiver = NULL;
smbox->cinfo = NULL;
}
return 0;
}
static int mailbox_send_message(struct scmi_chan_info *cinfo,
struct scmi_xfer *xfer)
{
struct scmi_mailbox *smbox = cinfo->transport_info;
int ret;
/*
* The mailbox layer has its own queue. However the mailbox queue
* confuses the per message SCMI timeouts since the clock starts when
* the message is submitted into the mailbox queue. So when multiple
* messages are queued up the clock starts on all messages instead of
* only the one inflight.
*/
mutex_lock(&smbox->chan_lock);
ret = mbox_send_message(smbox->chan, xfer);
/* mbox_send_message returns non-negative value on success */
if (ret < 0) {
mutex_unlock(&smbox->chan_lock);
return ret;
}
return 0;
}
static void mailbox_mark_txdone(struct scmi_chan_info *cinfo, int ret,
struct scmi_xfer *__unused)
{
struct scmi_mailbox *smbox = cinfo->transport_info;
mbox_client_txdone(smbox->chan, ret);
/* Release channel */
mutex_unlock(&smbox->chan_lock);
}
static void mailbox_fetch_response(struct scmi_chan_info *cinfo,
struct scmi_xfer *xfer)
{
struct scmi_mailbox *smbox = cinfo->transport_info;
core->shmem->fetch_response(smbox->shmem, xfer);
}
static void mailbox_fetch_notification(struct scmi_chan_info *cinfo,
size_t max_len, struct scmi_xfer *xfer)
{
struct scmi_mailbox *smbox = cinfo->transport_info;
core->shmem->fetch_notification(smbox->shmem, max_len, xfer);
}
static void mailbox_clear_channel(struct scmi_chan_info *cinfo)
{
struct scmi_mailbox *smbox = cinfo->transport_info;
struct mbox_chan *intr_chan;
int ret;
core->shmem->clear_channel(smbox->shmem);
if (!core->shmem->channel_intr_enabled(smbox->shmem))
return;
if (smbox->chan_platform_receiver)
intr_chan = smbox->chan_platform_receiver;
else if (smbox->chan)
intr_chan = smbox->chan;
else
return;
ret = mbox_send_message(intr_chan, NULL);
/* mbox_send_message returns non-negative value on success, so reset */
if (ret > 0)
ret = 0;
mbox_client_txdone(intr_chan, ret);
}
static bool
mailbox_poll_done(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
{
struct scmi_mailbox *smbox = cinfo->transport_info;
return core->shmem->poll_done(smbox->shmem, xfer);
}
static const struct scmi_transport_ops scmi_mailbox_ops = {
.chan_available = mailbox_chan_available,
.chan_setup = mailbox_chan_setup,
.chan_free = mailbox_chan_free,
.send_message = mailbox_send_message,
.mark_txdone = mailbox_mark_txdone,
.fetch_response = mailbox_fetch_response,
.fetch_notification = mailbox_fetch_notification,
.clear_channel = mailbox_clear_channel,
.poll_done = mailbox_poll_done,
};
static struct scmi_desc scmi_mailbox_desc = {
.ops = &scmi_mailbox_ops,
.max_rx_timeout_ms = 30, /* We may increase this if required */
.max_msg = 20, /* Limited by MBOX_TX_QUEUE_LEN */
.max_msg_size = 128,
};
static const struct of_device_id scmi_of_match[] = {
{ .compatible = "arm,scmi" },
{ /* Sentinel */ },
};
DEFINE_SCMI_TRANSPORT_DRIVER(scmi_mailbox, scmi_mailbox_driver,
scmi_mailbox_desc, scmi_of_match, core);
module_platform_driver(scmi_mailbox_driver);
MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
MODULE_DESCRIPTION("SCMI Mailbox Transport driver");
MODULE_LICENSE("GPL");
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