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Diffstat (limited to '')
| -rw-r--r-- | drivers/firmware/arm_scmi/virtio.c | 941 |
1 files changed, 941 insertions, 0 deletions
diff --git a/drivers/firmware/arm_scmi/virtio.c b/drivers/firmware/arm_scmi/virtio.c new file mode 100644 index 000000000..1db975c08 --- /dev/null +++ b/drivers/firmware/arm_scmi/virtio.c @@ -0,0 +1,941 @@ +// 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; + 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; + + /* + * Break device to inhibit further traffic flowing while shutting down + * the channels: doing it later holding vioch->lock creates unsafe + * locking dependency chains as reported by LOCKDEP. + */ + virtio_break_device(vioch->vqueue->vdev); + 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), +}; |