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936 lines
27 KiB
936 lines
27 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Virtio Transport driver for Arm System Control and Management Interface |
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* (SCMI). |
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* |
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* Copyright (C) 2020-2022 OpenSynergy. |
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* Copyright (C) 2021-2022 ARM Ltd. |
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*/ |
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|
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/** |
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* DOC: Theory of Operation |
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* |
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* The scmi-virtio transport implements a driver for the virtio SCMI device. |
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* |
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* There is one Tx channel (virtio cmdq, A2P channel) and at most one Rx |
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* channel (virtio eventq, P2A channel). Each channel is implemented through a |
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* virtqueue. Access to each virtqueue is protected by spinlocks. |
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*/ |
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|
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#include <linux/completion.h> |
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#include <linux/errno.h> |
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#include <linux/refcount.h> |
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#include <linux/slab.h> |
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#include <linux/virtio.h> |
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#include <linux/virtio_config.h> |
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|
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#include <uapi/linux/virtio_ids.h> |
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#include <uapi/linux/virtio_scmi.h> |
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|
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#include "common.h" |
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|
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#define VIRTIO_MAX_RX_TIMEOUT_MS 60000 |
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#define VIRTIO_SCMI_MAX_MSG_SIZE 128 /* Value may be increased. */ |
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#define VIRTIO_SCMI_MAX_PDU_SIZE \ |
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(VIRTIO_SCMI_MAX_MSG_SIZE + SCMI_MSG_MAX_PROT_OVERHEAD) |
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#define DESCRIPTORS_PER_TX_MSG 2 |
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|
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/** |
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* struct scmi_vio_channel - Transport channel information |
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* |
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* @vqueue: Associated virtqueue |
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* @cinfo: SCMI Tx or Rx channel |
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* @free_lock: Protects access to the @free_list. |
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* @free_list: List of unused scmi_vio_msg, maintained for Tx channels only |
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* @deferred_tx_work: Worker for TX deferred replies processing |
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* @deferred_tx_wq: Workqueue for TX deferred replies |
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* @pending_lock: Protects access to the @pending_cmds_list. |
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* @pending_cmds_list: List of pre-fetched commands queueud for later processing |
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* @is_rx: Whether channel is an Rx channel |
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* @max_msg: Maximum number of pending messages for this channel. |
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* @lock: Protects access to all members except users, free_list and |
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* pending_cmds_list. |
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* @shutdown_done: A reference to a completion used when freeing this channel. |
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* @users: A reference count to currently active users of this channel. |
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*/ |
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struct scmi_vio_channel { |
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struct virtqueue *vqueue; |
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struct scmi_chan_info *cinfo; |
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/* lock to protect access to the free list. */ |
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spinlock_t free_lock; |
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struct list_head free_list; |
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/* lock to protect access to the pending list. */ |
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spinlock_t pending_lock; |
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struct list_head pending_cmds_list; |
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struct work_struct deferred_tx_work; |
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struct workqueue_struct *deferred_tx_wq; |
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bool is_rx; |
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unsigned int max_msg; |
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/* |
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* Lock to protect access to all members except users, free_list and |
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* pending_cmds_list |
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*/ |
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spinlock_t lock; |
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struct completion *shutdown_done; |
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refcount_t users; |
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}; |
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|
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enum poll_states { |
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VIO_MSG_NOT_POLLED, |
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VIO_MSG_POLL_TIMEOUT, |
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VIO_MSG_POLLING, |
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VIO_MSG_POLL_DONE, |
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}; |
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|
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/** |
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* struct scmi_vio_msg - Transport PDU information |
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* |
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* @request: SDU used for commands |
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* @input: SDU used for (delayed) responses and notifications |
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* @list: List which scmi_vio_msg may be part of |
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* @rx_len: Input SDU size in bytes, once input has been received |
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* @poll_idx: Last used index registered for polling purposes if this message |
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* transaction reply was configured for polling. |
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* @poll_status: Polling state for this message. |
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* @poll_lock: A lock to protect @poll_status |
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* @users: A reference count to track this message users and avoid premature |
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* freeing (and reuse) when polling and IRQ execution paths interleave. |
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*/ |
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struct scmi_vio_msg { |
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struct scmi_msg_payld *request; |
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struct scmi_msg_payld *input; |
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struct list_head list; |
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unsigned int rx_len; |
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unsigned int poll_idx; |
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enum poll_states poll_status; |
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/* Lock to protect access to poll_status */ |
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spinlock_t poll_lock; |
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refcount_t users; |
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}; |
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|
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/* Only one SCMI VirtIO device can possibly exist */ |
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static struct virtio_device *scmi_vdev; |
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|
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static void scmi_vio_channel_ready(struct scmi_vio_channel *vioch, |
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struct scmi_chan_info *cinfo) |
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{ |
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unsigned long flags; |
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|
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spin_lock_irqsave(&vioch->lock, flags); |
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cinfo->transport_info = vioch; |
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/* Indirectly setting channel not available any more */ |
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vioch->cinfo = cinfo; |
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spin_unlock_irqrestore(&vioch->lock, flags); |
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|
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refcount_set(&vioch->users, 1); |
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} |
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|
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static inline bool scmi_vio_channel_acquire(struct scmi_vio_channel *vioch) |
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{ |
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return refcount_inc_not_zero(&vioch->users); |
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} |
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|
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static inline void scmi_vio_channel_release(struct scmi_vio_channel *vioch) |
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{ |
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if (refcount_dec_and_test(&vioch->users)) { |
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unsigned long flags; |
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|
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spin_lock_irqsave(&vioch->lock, flags); |
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if (vioch->shutdown_done) { |
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vioch->cinfo = NULL; |
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complete(vioch->shutdown_done); |
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} |
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spin_unlock_irqrestore(&vioch->lock, flags); |
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} |
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} |
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|
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static void scmi_vio_channel_cleanup_sync(struct scmi_vio_channel *vioch) |
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{ |
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unsigned long flags; |
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DECLARE_COMPLETION_ONSTACK(vioch_shutdown_done); |
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|
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/* |
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* Prepare to wait for the last release if not already released |
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* or in progress. |
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*/ |
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spin_lock_irqsave(&vioch->lock, flags); |
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if (!vioch->cinfo || vioch->shutdown_done) { |
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spin_unlock_irqrestore(&vioch->lock, flags); |
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return; |
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} |
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vioch->shutdown_done = &vioch_shutdown_done; |
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virtio_break_device(vioch->vqueue->vdev); |
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if (!vioch->is_rx && vioch->deferred_tx_wq) |
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/* Cannot be kicked anymore after this...*/ |
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vioch->deferred_tx_wq = NULL; |
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spin_unlock_irqrestore(&vioch->lock, flags); |
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scmi_vio_channel_release(vioch); |
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|
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/* Let any possibly concurrent RX path release the channel */ |
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wait_for_completion(vioch->shutdown_done); |
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} |
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|
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/* Assumes to be called with vio channel acquired already */ |
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static struct scmi_vio_msg * |
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scmi_virtio_get_free_msg(struct scmi_vio_channel *vioch) |
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{ |
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unsigned long flags; |
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struct scmi_vio_msg *msg; |
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|
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spin_lock_irqsave(&vioch->free_lock, flags); |
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if (list_empty(&vioch->free_list)) { |
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spin_unlock_irqrestore(&vioch->free_lock, flags); |
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return NULL; |
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} |
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|
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msg = list_first_entry(&vioch->free_list, typeof(*msg), list); |
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list_del_init(&msg->list); |
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spin_unlock_irqrestore(&vioch->free_lock, flags); |
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|
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/* Still no users, no need to acquire poll_lock */ |
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msg->poll_status = VIO_MSG_NOT_POLLED; |
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refcount_set(&msg->users, 1); |
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|
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return msg; |
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} |
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static inline bool scmi_vio_msg_acquire(struct scmi_vio_msg *msg) |
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{ |
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return refcount_inc_not_zero(&msg->users); |
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} |
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|
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/* Assumes to be called with vio channel acquired already */ |
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static inline bool scmi_vio_msg_release(struct scmi_vio_channel *vioch, |
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struct scmi_vio_msg *msg) |
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{ |
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bool ret; |
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ret = refcount_dec_and_test(&msg->users); |
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if (ret) { |
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unsigned long flags; |
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spin_lock_irqsave(&vioch->free_lock, flags); |
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list_add_tail(&msg->list, &vioch->free_list); |
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spin_unlock_irqrestore(&vioch->free_lock, flags); |
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} |
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return ret; |
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} |
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static bool scmi_vio_have_vq_rx(struct virtio_device *vdev) |
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{ |
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return virtio_has_feature(vdev, VIRTIO_SCMI_F_P2A_CHANNELS); |
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} |
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static int scmi_vio_feed_vq_rx(struct scmi_vio_channel *vioch, |
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struct scmi_vio_msg *msg) |
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{ |
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struct scatterlist sg_in; |
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int rc; |
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unsigned long flags; |
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struct device *dev = &vioch->vqueue->vdev->dev; |
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sg_init_one(&sg_in, msg->input, VIRTIO_SCMI_MAX_PDU_SIZE); |
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spin_lock_irqsave(&vioch->lock, flags); |
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rc = virtqueue_add_inbuf(vioch->vqueue, &sg_in, 1, msg, GFP_ATOMIC); |
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if (rc) |
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dev_err(dev, "failed to add to RX virtqueue (%d)\n", rc); |
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else |
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virtqueue_kick(vioch->vqueue); |
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spin_unlock_irqrestore(&vioch->lock, flags); |
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return rc; |
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} |
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/* |
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* Assume to be called with channel already acquired or not ready at all; |
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* vioch->lock MUST NOT have been already acquired. |
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*/ |
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static void scmi_finalize_message(struct scmi_vio_channel *vioch, |
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struct scmi_vio_msg *msg) |
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{ |
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if (vioch->is_rx) |
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scmi_vio_feed_vq_rx(vioch, msg); |
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else |
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scmi_vio_msg_release(vioch, msg); |
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} |
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static void scmi_vio_complete_cb(struct virtqueue *vqueue) |
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{ |
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unsigned long flags; |
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unsigned int length; |
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struct scmi_vio_channel *vioch; |
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struct scmi_vio_msg *msg; |
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bool cb_enabled = true; |
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if (WARN_ON_ONCE(!vqueue->vdev->priv)) |
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return; |
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vioch = &((struct scmi_vio_channel *)vqueue->vdev->priv)[vqueue->index]; |
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for (;;) { |
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if (!scmi_vio_channel_acquire(vioch)) |
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return; |
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spin_lock_irqsave(&vioch->lock, flags); |
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if (cb_enabled) { |
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virtqueue_disable_cb(vqueue); |
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cb_enabled = false; |
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} |
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msg = virtqueue_get_buf(vqueue, &length); |
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if (!msg) { |
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if (virtqueue_enable_cb(vqueue)) { |
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spin_unlock_irqrestore(&vioch->lock, flags); |
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scmi_vio_channel_release(vioch); |
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return; |
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} |
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cb_enabled = true; |
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} |
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spin_unlock_irqrestore(&vioch->lock, flags); |
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if (msg) { |
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msg->rx_len = length; |
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scmi_rx_callback(vioch->cinfo, |
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msg_read_header(msg->input), msg); |
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scmi_finalize_message(vioch, msg); |
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} |
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/* |
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* Release vio channel between loop iterations to allow |
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* virtio_chan_free() to eventually fully release it when |
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* shutting down; in such a case, any outstanding message will |
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* be ignored since this loop will bail out at the next |
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* iteration. |
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*/ |
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scmi_vio_channel_release(vioch); |
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} |
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} |
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static void scmi_vio_deferred_tx_worker(struct work_struct *work) |
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{ |
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unsigned long flags; |
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struct scmi_vio_channel *vioch; |
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struct scmi_vio_msg *msg, *tmp; |
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vioch = container_of(work, struct scmi_vio_channel, deferred_tx_work); |
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if (!scmi_vio_channel_acquire(vioch)) |
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return; |
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/* |
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* Process pre-fetched messages: these could be non-polled messages or |
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* late timed-out replies to polled messages dequeued by chance while |
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* polling for some other messages: this worker is in charge to process |
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* the valid non-expired messages and anyway finally free all of them. |
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*/ |
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spin_lock_irqsave(&vioch->pending_lock, flags); |
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|
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/* Scan the list of possibly pre-fetched messages during polling. */ |
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list_for_each_entry_safe(msg, tmp, &vioch->pending_cmds_list, list) { |
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list_del(&msg->list); |
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|
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/* |
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* Channel is acquired here (cannot vanish) and this message |
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* is no more processed elsewhere so no poll_lock needed. |
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*/ |
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if (msg->poll_status == VIO_MSG_NOT_POLLED) |
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scmi_rx_callback(vioch->cinfo, |
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msg_read_header(msg->input), msg); |
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|
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/* Free the processed message once done */ |
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scmi_vio_msg_release(vioch, msg); |
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} |
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spin_unlock_irqrestore(&vioch->pending_lock, flags); |
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|
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/* Process possibly still pending messages */ |
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scmi_vio_complete_cb(vioch->vqueue); |
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|
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scmi_vio_channel_release(vioch); |
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} |
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static const char *const scmi_vio_vqueue_names[] = { "tx", "rx" }; |
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|
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static vq_callback_t *scmi_vio_complete_callbacks[] = { |
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scmi_vio_complete_cb, |
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scmi_vio_complete_cb |
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}; |
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|
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static unsigned int virtio_get_max_msg(struct scmi_chan_info *base_cinfo) |
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{ |
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struct scmi_vio_channel *vioch = base_cinfo->transport_info; |
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|
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return vioch->max_msg; |
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} |
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|
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static int virtio_link_supplier(struct device *dev) |
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{ |
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if (!scmi_vdev) { |
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dev_notice(dev, |
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"Deferring probe after not finding a bound scmi-virtio device\n"); |
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return -EPROBE_DEFER; |
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} |
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|
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if (!device_link_add(dev, &scmi_vdev->dev, |
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DL_FLAG_AUTOREMOVE_CONSUMER)) { |
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dev_err(dev, "Adding link to supplier virtio device failed\n"); |
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return -ECANCELED; |
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} |
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|
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return 0; |
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} |
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|
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static bool virtio_chan_available(struct device *dev, int idx) |
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{ |
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struct scmi_vio_channel *channels, *vioch = NULL; |
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|
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if (WARN_ON_ONCE(!scmi_vdev)) |
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return false; |
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channels = (struct scmi_vio_channel *)scmi_vdev->priv; |
|
|
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switch (idx) { |
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case VIRTIO_SCMI_VQ_TX: |
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vioch = &channels[VIRTIO_SCMI_VQ_TX]; |
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break; |
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case VIRTIO_SCMI_VQ_RX: |
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if (scmi_vio_have_vq_rx(scmi_vdev)) |
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vioch = &channels[VIRTIO_SCMI_VQ_RX]; |
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break; |
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default: |
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return false; |
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} |
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|
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return vioch && !vioch->cinfo; |
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} |
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|
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static void scmi_destroy_tx_workqueue(void *deferred_tx_wq) |
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{ |
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destroy_workqueue(deferred_tx_wq); |
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} |
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|
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static int virtio_chan_setup(struct scmi_chan_info *cinfo, struct device *dev, |
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bool tx) |
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{ |
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struct scmi_vio_channel *vioch; |
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int index = tx ? VIRTIO_SCMI_VQ_TX : VIRTIO_SCMI_VQ_RX; |
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int i; |
|
|
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if (!scmi_vdev) |
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return -EPROBE_DEFER; |
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|
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vioch = &((struct scmi_vio_channel *)scmi_vdev->priv)[index]; |
|
|
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/* Setup a deferred worker for polling. */ |
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if (tx && !vioch->deferred_tx_wq) { |
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int ret; |
|
|
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vioch->deferred_tx_wq = |
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alloc_workqueue(dev_name(&scmi_vdev->dev), |
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WQ_UNBOUND | WQ_FREEZABLE | WQ_SYSFS, |
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0); |
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if (!vioch->deferred_tx_wq) |
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return -ENOMEM; |
|
|
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ret = devm_add_action_or_reset(dev, scmi_destroy_tx_workqueue, |
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vioch->deferred_tx_wq); |
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if (ret) |
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return ret; |
|
|
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INIT_WORK(&vioch->deferred_tx_work, |
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scmi_vio_deferred_tx_worker); |
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} |
|
|
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for (i = 0; i < vioch->max_msg; i++) { |
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struct scmi_vio_msg *msg; |
|
|
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msg = devm_kzalloc(dev, sizeof(*msg), GFP_KERNEL); |
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if (!msg) |
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return -ENOMEM; |
|
|
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if (tx) { |
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msg->request = devm_kzalloc(dev, |
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VIRTIO_SCMI_MAX_PDU_SIZE, |
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GFP_KERNEL); |
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if (!msg->request) |
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return -ENOMEM; |
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spin_lock_init(&msg->poll_lock); |
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refcount_set(&msg->users, 1); |
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} |
|
|
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msg->input = devm_kzalloc(dev, VIRTIO_SCMI_MAX_PDU_SIZE, |
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GFP_KERNEL); |
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if (!msg->input) |
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return -ENOMEM; |
|
|
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scmi_finalize_message(vioch, msg); |
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} |
|
|
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scmi_vio_channel_ready(vioch, cinfo); |
|
|
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return 0; |
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} |
|
|
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static int virtio_chan_free(int id, void *p, void *data) |
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{ |
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struct scmi_chan_info *cinfo = p; |
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struct scmi_vio_channel *vioch = cinfo->transport_info; |
|
|
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scmi_vio_channel_cleanup_sync(vioch); |
|
|
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scmi_free_channel(cinfo, data, id); |
|
|
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return 0; |
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} |
|
|
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static int virtio_send_message(struct scmi_chan_info *cinfo, |
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struct scmi_xfer *xfer) |
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{ |
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struct scmi_vio_channel *vioch = cinfo->transport_info; |
|
struct scatterlist sg_out; |
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struct scatterlist sg_in; |
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struct scatterlist *sgs[DESCRIPTORS_PER_TX_MSG] = { &sg_out, &sg_in }; |
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unsigned long flags; |
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int rc; |
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struct scmi_vio_msg *msg; |
|
|
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if (!scmi_vio_channel_acquire(vioch)) |
|
return -EINVAL; |
|
|
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msg = scmi_virtio_get_free_msg(vioch); |
|
if (!msg) { |
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scmi_vio_channel_release(vioch); |
|
return -EBUSY; |
|
} |
|
|
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msg_tx_prepare(msg->request, xfer); |
|
|
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sg_init_one(&sg_out, msg->request, msg_command_size(xfer)); |
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sg_init_one(&sg_in, msg->input, msg_response_size(xfer)); |
|
|
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spin_lock_irqsave(&vioch->lock, flags); |
|
|
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/* |
|
* 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 |
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* - grab an additional msg refcount for the poll-path |
|
*/ |
|
if (xfer->hdr.poll_completion) { |
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msg->poll_idx = virtqueue_enable_cb_prepare(vioch->vqueue); |
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/* Still no users, no need to acquire poll_lock */ |
|
msg->poll_status = VIO_MSG_POLLING; |
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scmi_vio_msg_acquire(msg); |
|
/* Ensure initialized msg is visibly bound to xfer */ |
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smp_store_mb(xfer->priv, msg); |
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} |
|
|
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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 |
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virtqueue_kick(vioch->vqueue); |
|
|
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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), |
|
};
|
|
|