blob: 33c9b81a55cd11926dad6426cd2e748052150f40 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* Virtio Transport driver for Arm System Control and Management Interface
* (SCMI).
*
* Copyright (C) 2020-2022 OpenSynergy.
* Copyright (C) 2021-2022 ARM Ltd.
*/
/**
* DOC: Theory of Operation
*
* The scmi-virtio transport implements a driver for the virtio SCMI device.
*
* There is one Tx channel (virtio cmdq, A2P channel) and at most one Rx
* channel (virtio eventq, P2A channel). Each channel is implemented through a
* virtqueue. Access to each virtqueue is protected by spinlocks.
*/
#include <linux/completion.h>
#include <linux/errno.h>
#include <linux/refcount.h>
#include <linux/slab.h>
#include <linux/virtio.h>
#include <linux/virtio_config.h>
#include <uapi/linux/virtio_ids.h>
#include <uapi/linux/virtio_scmi.h>
#include "common.h"
#define VIRTIO_MAX_RX_TIMEOUT_MS 60000
#define VIRTIO_SCMI_MAX_MSG_SIZE 128 /* Value may be increased. */
#define VIRTIO_SCMI_MAX_PDU_SIZE \
(VIRTIO_SCMI_MAX_MSG_SIZE + SCMI_MSG_MAX_PROT_OVERHEAD)
#define DESCRIPTORS_PER_TX_MSG 2
/**
* struct scmi_vio_channel - Transport channel information
*
* @vqueue: Associated virtqueue
* @cinfo: SCMI Tx or Rx channel
* @free_lock: Protects access to the @free_list.
* @free_list: List of unused scmi_vio_msg, maintained for Tx channels only
* @deferred_tx_work: Worker for TX deferred replies processing
* @deferred_tx_wq: Workqueue for TX deferred replies
* @pending_lock: Protects access to the @pending_cmds_list.
* @pending_cmds_list: List of pre-fetched commands queueud for later processing
* @is_rx: Whether channel is an Rx channel
* @max_msg: Maximum number of pending messages for this channel.
* @lock: Protects access to all members except users, free_list and
* pending_cmds_list.
* @shutdown_done: A reference to a completion used when freeing this channel.
* @users: A reference count to currently active users of this channel.
*/
struct scmi_vio_channel {
struct virtqueue *vqueue;
struct scmi_chan_info *cinfo;
/* lock to protect access to the free list. */
spinlock_t free_lock;
struct list_head free_list;
/* lock to protect access to the pending list. */
spinlock_t pending_lock;
struct list_head pending_cmds_list;
struct work_struct deferred_tx_work;
struct workqueue_struct *deferred_tx_wq;
bool is_rx;
unsigned int max_msg;
/*
* Lock to protect access to all members except users, free_list and
* pending_cmds_list
*/
spinlock_t lock;
struct completion *shutdown_done;
refcount_t users;
};
enum poll_states {
VIO_MSG_NOT_POLLED,
VIO_MSG_POLL_TIMEOUT,
VIO_MSG_POLLING,
VIO_MSG_POLL_DONE,
};
/**
* struct scmi_vio_msg - Transport PDU information
*
* @request: SDU used for commands
* @input: SDU used for (delayed) responses and notifications
* @list: List which scmi_vio_msg may be part of
* @rx_len: Input SDU size in bytes, once input has been received
* @poll_idx: Last used index registered for polling purposes if this message
* transaction reply was configured for polling.
* @poll_status: Polling state for this message.
* @poll_lock: A lock to protect @poll_status
* @users: A reference count to track this message users and avoid premature
* freeing (and reuse) when polling and IRQ execution paths interleave.
*/
struct scmi_vio_msg {
struct scmi_msg_payld *request;
struct scmi_msg_payld *input;
struct list_head list;
unsigned int rx_len;
unsigned int poll_idx;
enum poll_states poll_status;
/* Lock to protect access to poll_status */
spinlock_t poll_lock;
refcount_t users;
};
/* Only one SCMI VirtIO device can possibly exist */
static struct virtio_device *scmi_vdev;
static void scmi_vio_channel_ready(struct scmi_vio_channel *vioch,
struct scmi_chan_info *cinfo)
{
unsigned long flags;
spin_lock_irqsave(&vioch->lock, flags);
cinfo->transport_info = vioch;
/* Indirectly setting channel not available any more */
vioch->cinfo = cinfo;
spin_unlock_irqrestore(&vioch->lock, flags);
refcount_set(&vioch->users, 1);
}
static inline bool scmi_vio_channel_acquire(struct scmi_vio_channel *vioch)
{
return refcount_inc_not_zero(&vioch->users);
}
static inline void scmi_vio_channel_release(struct scmi_vio_channel *vioch)
{
if (refcount_dec_and_test(&vioch->users)) {
unsigned long flags;
spin_lock_irqsave(&vioch->lock, flags);
if (vioch->shutdown_done) {
vioch->cinfo = NULL;
complete(vioch->shutdown_done);
}
spin_unlock_irqrestore(&vioch->lock, flags);
}
}
static void scmi_vio_channel_cleanup_sync(struct scmi_vio_channel *vioch)
{
unsigned long flags;
DECLARE_COMPLETION_ONSTACK(vioch_shutdown_done);
/*
* Prepare to wait for the last release if not already released
* or in progress.
*/
spin_lock_irqsave(&vioch->lock, flags);
if (!vioch->cinfo || vioch->shutdown_done) {
spin_unlock_irqrestore(&vioch->lock, flags);
return;
}
vioch->shutdown_done = &vioch_shutdown_done;
virtio_break_device(vioch->vqueue->vdev);
if (!vioch->is_rx && vioch->deferred_tx_wq)
/* Cannot be kicked anymore after this...*/
vioch->deferred_tx_wq = NULL;
spin_unlock_irqrestore(&vioch->lock, flags);
scmi_vio_channel_release(vioch);
/* Let any possibly concurrent RX path release the channel */
wait_for_completion(vioch->shutdown_done);
}
/* Assumes to be called with vio channel acquired already */
static struct scmi_vio_msg *
scmi_virtio_get_free_msg(struct scmi_vio_channel *vioch)
{
unsigned long flags;
struct scmi_vio_msg *msg;
spin_lock_irqsave(&vioch->free_lock, flags);
if (list_empty(&vioch->free_list)) {
spin_unlock_irqrestore(&vioch->free_lock, flags);
return NULL;
}
msg = list_first_entry(&vioch->free_list, typeof(*msg), list);
list_del_init(&msg->list);
spin_unlock_irqrestore(&vioch->free_lock, flags);
/* Still no users, no need to acquire poll_lock */
msg->poll_status = VIO_MSG_NOT_POLLED;
refcount_set(&msg->users, 1);
return msg;
}
static inline bool scmi_vio_msg_acquire(struct scmi_vio_msg *msg)
{
return refcount_inc_not_zero(&msg->users);
}
/* Assumes to be called with vio channel acquired already */
static inline bool scmi_vio_msg_release(struct scmi_vio_channel *vioch,
struct scmi_vio_msg *msg)
{
bool ret;
ret = refcount_dec_and_test(&msg->users);
if (ret) {
unsigned long flags;
spin_lock_irqsave(&vioch->free_lock, flags);
list_add_tail(&msg->list, &vioch->free_list);
spin_unlock_irqrestore(&vioch->free_lock, flags);
}
return ret;
}
static bool scmi_vio_have_vq_rx(struct virtio_device *vdev)
{
return virtio_has_feature(vdev, VIRTIO_SCMI_F_P2A_CHANNELS);
}
static int scmi_vio_feed_vq_rx(struct scmi_vio_channel *vioch,
struct scmi_vio_msg *msg)
{
struct scatterlist sg_in;
int rc;
unsigned long flags;
struct device *dev = &vioch->vqueue->vdev->dev;
sg_init_one(&sg_in, msg->input, VIRTIO_SCMI_MAX_PDU_SIZE);
spin_lock_irqsave(&vioch->lock, flags);
rc = virtqueue_add_inbuf(vioch->vqueue, &sg_in, 1, msg, GFP_ATOMIC);
if (rc)
dev_err(dev, "failed to add to RX virtqueue (%d)\n", rc);
else
virtqueue_kick(vioch->vqueue);
spin_unlock_irqrestore(&vioch->lock, flags);
return rc;
}
/*
* Assume to be called with channel already acquired or not ready at all;
* vioch->lock MUST NOT have been already acquired.
*/
static void scmi_finalize_message(struct scmi_vio_channel *vioch,
struct scmi_vio_msg *msg)
{
if (vioch->is_rx)
scmi_vio_feed_vq_rx(vioch, msg);
else
scmi_vio_msg_release(vioch, msg);
}
static void scmi_vio_complete_cb(struct virtqueue *vqueue)
{
unsigned long flags;
unsigned int length;
struct scmi_vio_channel *vioch;
struct scmi_vio_msg *msg;
bool cb_enabled = true;
if (WARN_ON_ONCE(!vqueue->vdev->priv))
return;
vioch = &((struct scmi_vio_channel *)vqueue->vdev->priv)[vqueue->index];
for (;;) {
if (!scmi_vio_channel_acquire(vioch))
return;
spin_lock_irqsave(&vioch->lock, flags);
if (cb_enabled) {
virtqueue_disable_cb(vqueue);
cb_enabled = false;
}
msg = virtqueue_get_buf(vqueue, &length);
if (!msg) {
if (virtqueue_enable_cb(vqueue)) {
spin_unlock_irqrestore(&vioch->lock, flags);
scmi_vio_channel_release(vioch);
return;
}
cb_enabled = true;
}
spin_unlock_irqrestore(&vioch->lock, flags);
if (msg) {
msg->rx_len = length;
scmi_rx_callback(vioch->cinfo,
msg_read_header(msg->input), msg);
scmi_finalize_message(vioch, msg);
}
/*
* Release vio channel between loop iterations to allow
* virtio_chan_free() to eventually fully release it when
* shutting down; in such a case, any outstanding message will
* be ignored since this loop will bail out at the next
* iteration.
*/
scmi_vio_channel_release(vioch);
}
}
static void scmi_vio_deferred_tx_worker(struct work_struct *work)
{
unsigned long flags;
struct scmi_vio_channel *vioch;
struct scmi_vio_msg *msg, *tmp;
vioch = container_of(work, struct scmi_vio_channel, deferred_tx_work);
if (!scmi_vio_channel_acquire(vioch))
return;
/*
* Process pre-fetched messages: these could be non-polled messages or
* late timed-out replies to polled messages dequeued by chance while
* polling for some other messages: this worker is in charge to process
* the valid non-expired messages and anyway finally free all of them.
*/
spin_lock_irqsave(&vioch->pending_lock, flags);
/* Scan the list of possibly pre-fetched messages during polling. */
list_for_each_entry_safe(msg, tmp, &vioch->pending_cmds_list, list) {
list_del(&msg->list);
/*
* Channel is acquired here (cannot vanish) and this message
* is no more processed elsewhere so no poll_lock needed.
*/
if (msg->poll_status == VIO_MSG_NOT_POLLED)
scmi_rx_callback(vioch->cinfo,
msg_read_header(msg->input), msg);
/* Free the processed message once done */
scmi_vio_msg_release(vioch, msg);
}
spin_unlock_irqrestore(&vioch->pending_lock, flags);
/* Process possibly still pending messages */
scmi_vio_complete_cb(vioch->vqueue);
scmi_vio_channel_release(vioch);
}
static const char *const scmi_vio_vqueue_names[] = { "tx", "rx" };
static vq_callback_t *scmi_vio_complete_callbacks[] = {
scmi_vio_complete_cb,
scmi_vio_complete_cb
};
static unsigned int virtio_get_max_msg(struct scmi_chan_info *base_cinfo)
{
struct scmi_vio_channel *vioch = base_cinfo->transport_info;
return vioch->max_msg;
}
static int virtio_link_supplier(struct device *dev)
{
if (!scmi_vdev) {
dev_notice(dev,
"Deferring probe after not finding a bound scmi-virtio device\n");
return -EPROBE_DEFER;
}
if (!device_link_add(dev, &scmi_vdev->dev,
DL_FLAG_AUTOREMOVE_CONSUMER)) {
dev_err(dev, "Adding link to supplier virtio device failed\n");
return -ECANCELED;
}
return 0;
}
static bool virtio_chan_available(struct device *dev, int idx)
{
struct scmi_vio_channel *channels, *vioch = NULL;
if (WARN_ON_ONCE(!scmi_vdev))
return false;
channels = (struct scmi_vio_channel *)scmi_vdev->priv;
switch (idx) {
case VIRTIO_SCMI_VQ_TX:
vioch = &channels[VIRTIO_SCMI_VQ_TX];
break;
case VIRTIO_SCMI_VQ_RX:
if (scmi_vio_have_vq_rx(scmi_vdev))
vioch = &channels[VIRTIO_SCMI_VQ_RX];
break;
default:
return false;
}
return vioch && !vioch->cinfo;
}
static void scmi_destroy_tx_workqueue(void *deferred_tx_wq)
{
destroy_workqueue(deferred_tx_wq);
}
static int virtio_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
bool tx)
{
struct scmi_vio_channel *vioch;
int index = tx ? VIRTIO_SCMI_VQ_TX : VIRTIO_SCMI_VQ_RX;
int i;
if (!scmi_vdev)
return -EPROBE_DEFER;
vioch = &((struct scmi_vio_channel *)scmi_vdev->priv)[index];
/* Setup a deferred worker for polling. */
if (tx && !vioch->deferred_tx_wq) {
int ret;
vioch->deferred_tx_wq =
alloc_workqueue(dev_name(&scmi_vdev->dev),
WQ_UNBOUND | WQ_FREEZABLE | WQ_SYSFS,
0);
if (!vioch->deferred_tx_wq)
return -ENOMEM;
ret = devm_add_action_or_reset(dev, scmi_destroy_tx_workqueue,
vioch->deferred_tx_wq);
if (ret)
return ret;
INIT_WORK(&vioch->deferred_tx_work,
scmi_vio_deferred_tx_worker);
}
for (i = 0; i < vioch->max_msg; i++) {
struct scmi_vio_msg *msg;
msg = devm_kzalloc(dev, sizeof(*msg), GFP_KERNEL);
if (!msg)
return -ENOMEM;
if (tx) {
msg->request = devm_kzalloc(dev,
VIRTIO_SCMI_MAX_PDU_SIZE,
GFP_KERNEL);
if (!msg->request)
return -ENOMEM;
spin_lock_init(&msg->poll_lock);
refcount_set(&msg->users, 1);
}
msg->input = devm_kzalloc(dev, VIRTIO_SCMI_MAX_PDU_SIZE,
GFP_KERNEL);
if (!msg->input)
return -ENOMEM;
scmi_finalize_message(vioch, msg);
}
scmi_vio_channel_ready(vioch, cinfo);
return 0;
}
static int virtio_chan_free(int id, void *p, void *data)
{
struct scmi_chan_info *cinfo = p;
struct scmi_vio_channel *vioch = cinfo->transport_info;
scmi_vio_channel_cleanup_sync(vioch);
scmi_free_channel(cinfo, data, id);
return 0;
}
static int virtio_send_message(struct scmi_chan_info *cinfo,
struct scmi_xfer *xfer)
{
struct scmi_vio_channel *vioch = cinfo->transport_info;
struct scatterlist sg_out;
struct scatterlist sg_in;
struct scatterlist *sgs[DESCRIPTORS_PER_TX_MSG] = { &sg_out, &sg_in };
unsigned long flags;
int rc;
struct scmi_vio_msg *msg;
if (!scmi_vio_channel_acquire(vioch))
return -EINVAL;
msg = scmi_virtio_get_free_msg(vioch);
if (!msg) {
scmi_vio_channel_release(vioch);
return -EBUSY;
}
msg_tx_prepare(msg->request, xfer);
sg_init_one(&sg_out, msg->request, msg_command_size(xfer));
sg_init_one(&sg_in, msg->input, msg_response_size(xfer));
spin_lock_irqsave(&vioch->lock, flags);
/*
* If polling was requested for this transaction:
* - retrieve last used index (will be used as polling reference)
* - bind the polled message to the xfer via .priv
* - grab an additional msg refcount for the poll-path
*/
if (xfer->hdr.poll_completion) {
msg->poll_idx = virtqueue_enable_cb_prepare(vioch->vqueue);
/* Still no users, no need to acquire poll_lock */
msg->poll_status = VIO_MSG_POLLING;
scmi_vio_msg_acquire(msg);
/* Ensure initialized msg is visibly bound to xfer */
smp_store_mb(xfer->priv, msg);
}
rc = virtqueue_add_sgs(vioch->vqueue, sgs, 1, 1, msg, GFP_ATOMIC);
if (rc)
dev_err(vioch->cinfo->dev,
"failed to add to TX virtqueue (%d)\n", rc);
else
virtqueue_kick(vioch->vqueue);
spin_unlock_irqrestore(&vioch->lock, flags);
if (rc) {
/* Ensure order between xfer->priv clear and vq feeding */
smp_store_mb(xfer->priv, NULL);
if (xfer->hdr.poll_completion)
scmi_vio_msg_release(vioch, msg);
scmi_vio_msg_release(vioch, msg);
}
scmi_vio_channel_release(vioch);
return rc;
}
static void virtio_fetch_response(struct scmi_chan_info *cinfo,
struct scmi_xfer *xfer)
{
struct scmi_vio_msg *msg = xfer->priv;
if (msg)
msg_fetch_response(msg->input, msg->rx_len, xfer);
}
static void virtio_fetch_notification(struct scmi_chan_info *cinfo,
size_t max_len, struct scmi_xfer *xfer)
{
struct scmi_vio_msg *msg = xfer->priv;
if (msg)
msg_fetch_notification(msg->input, msg->rx_len, max_len, xfer);
}
/**
* virtio_mark_txdone - Mark transmission done
*
* Free only completed polling transfer messages.
*
* Note that in the SCMI VirtIO transport we never explicitly release still
* outstanding but timed-out messages by forcibly re-adding them to the
* free-list inside the TX code path; we instead let IRQ/RX callbacks, or the
* TX deferred worker, eventually clean up such messages once, finally, a late
* reply is received and discarded (if ever).
*
* This approach was deemed preferable since those pending timed-out buffers are
* still effectively owned by the SCMI platform VirtIO device even after timeout
* expiration: forcibly freeing and reusing them before they had been returned
* explicitly by the SCMI platform could lead to subtle bugs due to message
* corruption.
* An SCMI platform VirtIO device which never returns message buffers is
* anyway broken and it will quickly lead to exhaustion of available messages.
*
* For this same reason, here, we take care to free only the polled messages
* that had been somehow replied (only if not by chance already processed on the
* IRQ path - the initial scmi_vio_msg_release() takes care of this) and also
* any timed-out polled message if that indeed appears to have been at least
* dequeued from the virtqueues (VIO_MSG_POLL_DONE): this is needed since such
* messages won't be freed elsewhere. Any other polled message is marked as
* VIO_MSG_POLL_TIMEOUT.
*
* Possible late replies to timed-out polled messages will be eventually freed
* by RX callbacks if delivered on the IRQ path or by the deferred TX worker if
* dequeued on some other polling path.
*
* @cinfo: SCMI channel info
* @ret: Transmission return code
* @xfer: Transfer descriptor
*/
static void virtio_mark_txdone(struct scmi_chan_info *cinfo, int ret,
struct scmi_xfer *xfer)
{
unsigned long flags;
struct scmi_vio_channel *vioch = cinfo->transport_info;
struct scmi_vio_msg *msg = xfer->priv;
if (!msg || !scmi_vio_channel_acquire(vioch))
return;
/* Ensure msg is unbound from xfer anyway at this point */
smp_store_mb(xfer->priv, NULL);
/* Must be a polled xfer and not already freed on the IRQ path */
if (!xfer->hdr.poll_completion || scmi_vio_msg_release(vioch, msg)) {
scmi_vio_channel_release(vioch);
return;
}
spin_lock_irqsave(&msg->poll_lock, flags);
/* Do not free timedout polled messages only if still inflight */
if (ret != -ETIMEDOUT || msg->poll_status == VIO_MSG_POLL_DONE)
scmi_vio_msg_release(vioch, msg);
else if (msg->poll_status == VIO_MSG_POLLING)
msg->poll_status = VIO_MSG_POLL_TIMEOUT;
spin_unlock_irqrestore(&msg->poll_lock, flags);
scmi_vio_channel_release(vioch);
}
/**
* virtio_poll_done - Provide polling support for VirtIO transport
*
* @cinfo: SCMI channel info
* @xfer: Reference to the transfer being poll for.
*
* VirtIO core provides a polling mechanism based only on last used indexes:
* this means that it is possible to poll the virtqueues waiting for something
* new to arrive from the host side, but the only way to check if the freshly
* arrived buffer was indeed what we were waiting for is to compare the newly
* arrived message descriptor with the one we are polling on.
*
* As a consequence it can happen to dequeue something different from the buffer
* we were poll-waiting for: if that is the case such early fetched buffers are
* then added to a the @pending_cmds_list list for later processing by a
* dedicated deferred worker.
*
* So, basically, once something new is spotted we proceed to de-queue all the
* freshly received used buffers until we found the one we were polling on, or,
* we have 'seemingly' emptied the virtqueue; if some buffers are still pending
* in the vqueue at the end of the polling loop (possible due to inherent races
* in virtqueues handling mechanisms), we similarly kick the deferred worker
* and let it process those, to avoid indefinitely looping in the .poll_done
* busy-waiting helper.
*
* Finally, we delegate to the deferred worker also the final free of any timed
* out reply to a polled message that we should dequeue.
*
* Note that, since we do NOT have per-message suppress notification mechanism,
* the message we are polling for could be alternatively delivered via usual
* IRQs callbacks on another core which happened to have IRQs enabled while we
* are actively polling for it here: in such a case it will be handled as such
* by scmi_rx_callback() and the polling loop in the SCMI Core TX path will be
* transparently terminated anyway.
*
* Return: True once polling has successfully completed.
*/
static bool virtio_poll_done(struct scmi_chan_info *cinfo,
struct scmi_xfer *xfer)
{
bool pending, found = false;
unsigned int length, any_prefetched = 0;
unsigned long flags;
struct scmi_vio_msg *next_msg, *msg = xfer->priv;
struct scmi_vio_channel *vioch = cinfo->transport_info;
if (!msg)
return true;
/*
* Processed already by other polling loop on another CPU ?
*
* Note that this message is acquired on the poll path so cannot vanish
* while inside this loop iteration even if concurrently processed on
* the IRQ path.
*
* Avoid to acquire poll_lock since polled_status can be changed
* in a relevant manner only later in this same thread of execution:
* any other possible changes made concurrently by other polling loops
* or by a reply delivered on the IRQ path have no meaningful impact on
* this loop iteration: in other words it is harmless to allow this
* possible race but let has avoid spinlocking with irqs off in this
* initial part of the polling loop.
*/
if (msg->poll_status == VIO_MSG_POLL_DONE)
return true;
if (!scmi_vio_channel_acquire(vioch))
return true;
/* Has cmdq index moved at all ? */
pending = virtqueue_poll(vioch->vqueue, msg->poll_idx);
if (!pending) {
scmi_vio_channel_release(vioch);
return false;
}
spin_lock_irqsave(&vioch->lock, flags);
virtqueue_disable_cb(vioch->vqueue);
/*
* Process all new messages till the polled-for message is found OR
* the vqueue is empty.
*/
while ((next_msg = virtqueue_get_buf(vioch->vqueue, &length))) {
bool next_msg_done = false;
/*
* Mark any dequeued buffer message as VIO_MSG_POLL_DONE so
* that can be properly freed even on timeout in mark_txdone.
*/
spin_lock(&next_msg->poll_lock);
if (next_msg->poll_status == VIO_MSG_POLLING) {
next_msg->poll_status = VIO_MSG_POLL_DONE;
next_msg_done = true;
}
spin_unlock(&next_msg->poll_lock);
next_msg->rx_len = length;
/* Is the message we were polling for ? */
if (next_msg == msg) {
found = true;
break;
} else if (next_msg_done) {
/* Skip the rest if this was another polled msg */
continue;
}
/*
* Enqueue for later processing any non-polled message and any
* timed-out polled one that we happen to have dequeued.
*/
spin_lock(&next_msg->poll_lock);
if (next_msg->poll_status == VIO_MSG_NOT_POLLED ||
next_msg->poll_status == VIO_MSG_POLL_TIMEOUT) {
spin_unlock(&next_msg->poll_lock);
any_prefetched++;
spin_lock(&vioch->pending_lock);
list_add_tail(&next_msg->list,
&vioch->pending_cmds_list);
spin_unlock(&vioch->pending_lock);
} else {
spin_unlock(&next_msg->poll_lock);
}
}
/*
* When the polling loop has successfully terminated if something
* else was queued in the meantime, it will be served by a deferred
* worker OR by the normal IRQ/callback OR by other poll loops.
*
* If we are still looking for the polled reply, the polling index has
* to be updated to the current vqueue last used index.
*/
if (found) {
pending = !virtqueue_enable_cb(vioch->vqueue);
} else {
msg->poll_idx = virtqueue_enable_cb_prepare(vioch->vqueue);
pending = virtqueue_poll(vioch->vqueue, msg->poll_idx);
}
if (vioch->deferred_tx_wq && (any_prefetched || pending))
queue_work(vioch->deferred_tx_wq, &vioch->deferred_tx_work);
spin_unlock_irqrestore(&vioch->lock, flags);
scmi_vio_channel_release(vioch);
return found;
}
static const struct scmi_transport_ops scmi_virtio_ops = {
.link_supplier = virtio_link_supplier,
.chan_available = virtio_chan_available,
.chan_setup = virtio_chan_setup,
.chan_free = virtio_chan_free,
.get_max_msg = virtio_get_max_msg,
.send_message = virtio_send_message,
.fetch_response = virtio_fetch_response,
.fetch_notification = virtio_fetch_notification,
.mark_txdone = virtio_mark_txdone,
.poll_done = virtio_poll_done,
};
static int scmi_vio_probe(struct virtio_device *vdev)
{
struct device *dev = &vdev->dev;
struct scmi_vio_channel *channels;
bool have_vq_rx;
int vq_cnt;
int i;
int ret;
struct virtqueue *vqs[VIRTIO_SCMI_VQ_MAX_CNT];
/* Only one SCMI VirtiO device allowed */
if (scmi_vdev) {
dev_err(dev,
"One SCMI Virtio device was already initialized: only one allowed.\n");
return -EBUSY;
}
have_vq_rx = scmi_vio_have_vq_rx(vdev);
vq_cnt = have_vq_rx ? VIRTIO_SCMI_VQ_MAX_CNT : 1;
channels = devm_kcalloc(dev, vq_cnt, sizeof(*channels), GFP_KERNEL);
if (!channels)
return -ENOMEM;
if (have_vq_rx)
channels[VIRTIO_SCMI_VQ_RX].is_rx = true;
ret = virtio_find_vqs(vdev, vq_cnt, vqs, scmi_vio_complete_callbacks,
scmi_vio_vqueue_names, NULL);
if (ret) {
dev_err(dev, "Failed to get %d virtqueue(s)\n", vq_cnt);
return ret;
}
for (i = 0; i < vq_cnt; i++) {
unsigned int sz;
spin_lock_init(&channels[i].lock);
spin_lock_init(&channels[i].free_lock);
INIT_LIST_HEAD(&channels[i].free_list);
spin_lock_init(&channels[i].pending_lock);
INIT_LIST_HEAD(&channels[i].pending_cmds_list);
channels[i].vqueue = vqs[i];
sz = virtqueue_get_vring_size(channels[i].vqueue);
/* Tx messages need multiple descriptors. */
if (!channels[i].is_rx)
sz /= DESCRIPTORS_PER_TX_MSG;
if (sz > MSG_TOKEN_MAX) {
dev_info(dev,
"%s virtqueue could hold %d messages. Only %ld allowed to be pending.\n",
channels[i].is_rx ? "rx" : "tx",
sz, MSG_TOKEN_MAX);
sz = MSG_TOKEN_MAX;
}
channels[i].max_msg = sz;
}
vdev->priv = channels;
/* Ensure initialized scmi_vdev is visible */
smp_store_mb(scmi_vdev, vdev);
return 0;
}
static void scmi_vio_remove(struct virtio_device *vdev)
{
/*
* Once we get here, virtio_chan_free() will have already been called by
* the SCMI core for any existing channel and, as a consequence, all the
* virtio channels will have been already marked NOT ready, causing any
* outstanding message on any vqueue to be ignored by complete_cb: now
* we can just stop processing buffers and destroy the vqueues.
*/
virtio_reset_device(vdev);
vdev->config->del_vqs(vdev);
/* Ensure scmi_vdev is visible as NULL */
smp_store_mb(scmi_vdev, NULL);
}
static int scmi_vio_validate(struct virtio_device *vdev)
{
#ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO_VERSION1_COMPLIANCE
if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
dev_err(&vdev->dev,
"device does not comply with spec version 1.x\n");
return -EINVAL;
}
#endif
return 0;
}
static unsigned int features[] = {
VIRTIO_SCMI_F_P2A_CHANNELS,
};
static const struct virtio_device_id id_table[] = {
{ VIRTIO_ID_SCMI, VIRTIO_DEV_ANY_ID },
{ 0 }
};
static struct virtio_driver virtio_scmi_driver = {
.driver.name = "scmi-virtio",
.driver.owner = THIS_MODULE,
.feature_table = features,
.feature_table_size = ARRAY_SIZE(features),
.id_table = id_table,
.probe = scmi_vio_probe,
.remove = scmi_vio_remove,
.validate = scmi_vio_validate,
};
static int __init virtio_scmi_init(void)
{
return register_virtio_driver(&virtio_scmi_driver);
}
static void virtio_scmi_exit(void)
{
unregister_virtio_driver(&virtio_scmi_driver);
}
const struct scmi_desc scmi_virtio_desc = {
.transport_init = virtio_scmi_init,
.transport_exit = virtio_scmi_exit,
.ops = &scmi_virtio_ops,
/* for non-realtime virtio devices */
.max_rx_timeout_ms = VIRTIO_MAX_RX_TIMEOUT_MS,
.max_msg = 0, /* overridden by virtio_get_max_msg() */
.max_msg_size = VIRTIO_SCMI_MAX_MSG_SIZE,
.atomic_enabled = IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_VIRTIO_ATOMIC_ENABLE),
};