2021-08-03 13:10:24 +00:00
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// 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) 2020-2021 OpenSynergy.
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* Copyright (C) 2021 ARM Ltd.
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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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#include <linux/errno.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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#include <uapi/linux/virtio_ids.h>
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#include <uapi/linux/virtio_scmi.h>
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#include "common.h"
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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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* 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_list: List of unused scmi_vio_msg, maintained for Tx channels only
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* @is_rx: Whether channel is an Rx channel
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* @ready: Whether transport user is ready to hear about 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 ready.
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* @ready_lock: Protects access to ready. If required, it must be taken before
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* lock.
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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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struct list_head free_list;
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bool is_rx;
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bool ready;
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unsigned int max_msg;
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/* lock to protect access to all members except ready. */
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spinlock_t lock;
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/* lock to rotects access to ready flag. */
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spinlock_t ready_lock;
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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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*/
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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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};
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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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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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2021-11-12 18:07:05 +00:00
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struct scmi_vio_msg *msg,
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struct device *dev)
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2021-08-03 13:10:24 +00:00
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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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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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2021-11-12 18:07:05 +00:00
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dev_err_once(dev, "failed to add to virtqueue (%d)\n", rc);
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2021-08-03 13:10:24 +00:00
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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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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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2021-11-12 18:07:05 +00:00
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scmi_vio_feed_vq_rx(vioch, msg, vioch->cinfo->dev);
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2021-08-03 13:10:24 +00:00
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} else {
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2021-09-16 10:33:35 +00:00
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/* Here IRQs are assumed to be already disabled by the caller */
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spin_lock(&vioch->lock);
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2021-08-03 13:10:24 +00:00
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list_add(&msg->list, &vioch->free_list);
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2021-09-16 10:33:35 +00:00
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spin_unlock(&vioch->lock);
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2021-08-03 13:10:24 +00:00
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}
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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 ready_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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spin_lock_irqsave(&vioch->ready_lock, ready_flags);
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if (!vioch->ready) {
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if (!cb_enabled)
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(void)virtqueue_enable_cb(vqueue);
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goto unlock_ready_out;
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}
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2021-09-16 10:33:35 +00:00
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/* IRQs already disabled here no need to irqsave */
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spin_lock(&vioch->lock);
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2021-08-03 13:10:24 +00:00
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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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goto unlock_out;
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cb_enabled = true;
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}
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2021-09-16 10:33:35 +00:00
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spin_unlock(&vioch->lock);
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2021-08-03 13:10:24 +00:00
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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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2021-09-16 10:33:35 +00:00
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/*
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* Release ready_lock and re-enable IRQs between loop iterations
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* to allow virtio_chan_free() to possibly kick in and set the
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* flag vioch->ready to false even in between processing of
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* messages, so as to force outstanding messages to be ignored
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* when system is shutting down.
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*/
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2021-08-03 13:10:24 +00:00
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spin_unlock_irqrestore(&vioch->ready_lock, ready_flags);
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}
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unlock_out:
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2021-09-16 10:33:35 +00:00
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spin_unlock(&vioch->lock);
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2021-08-03 13:10:24 +00:00
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unlock_ready_out:
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spin_unlock_irqrestore(&vioch->ready_lock, ready_flags);
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}
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static const char *const scmi_vio_vqueue_names[] = { "tx", "rx" };
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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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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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return vioch->max_msg;
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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_once(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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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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return 0;
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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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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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2021-08-07 17:31:27 +00:00
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return vioch && !vioch->cinfo;
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2021-08-03 13:10:24 +00:00
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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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unsigned long flags;
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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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vioch = &((struct scmi_vio_channel *)scmi_vdev->priv)[index];
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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(cinfo->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(cinfo->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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}
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msg->input = devm_kzalloc(cinfo->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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if (tx) {
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spin_lock_irqsave(&vioch->lock, flags);
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list_add_tail(&msg->list, &vioch->free_list);
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spin_unlock_irqrestore(&vioch->lock, flags);
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} else {
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2021-11-12 18:07:05 +00:00
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scmi_vio_feed_vq_rx(vioch, msg, cinfo->dev);
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2021-08-03 13:10:24 +00:00
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}
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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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spin_lock_irqsave(&vioch->ready_lock, flags);
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vioch->ready = true;
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spin_unlock_irqrestore(&vioch->ready_lock, flags);
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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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unsigned long flags;
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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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spin_lock_irqsave(&vioch->ready_lock, flags);
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vioch->ready = false;
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spin_unlock_irqrestore(&vioch->ready_lock, flags);
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scmi_free_channel(cinfo, data, id);
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spin_lock_irqsave(&vioch->lock, flags);
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vioch->cinfo = NULL;
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spin_unlock_irqrestore(&vioch->lock, flags);
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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;
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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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spin_lock_irqsave(&vioch->lock, flags);
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if (list_empty(&vioch->free_list)) {
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spin_unlock_irqrestore(&vioch->lock, flags);
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return -EBUSY;
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}
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msg = list_first_entry(&vioch->free_list, typeof(*msg), list);
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list_del(&msg->list);
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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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rc = virtqueue_add_sgs(vioch->vqueue, sgs, 1, 1, msg, GFP_ATOMIC);
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if (rc) {
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list_add(&msg->list, &vioch->free_list);
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dev_err_once(vioch->cinfo->dev,
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"%s() failed to add to virtqueue (%d)\n", __func__,
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rc);
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} else {
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virtqueue_kick(vioch->vqueue);
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}
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spin_unlock_irqrestore(&vioch->lock, flags);
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return rc;
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}
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static void virtio_fetch_response(struct scmi_chan_info *cinfo,
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struct scmi_xfer *xfer)
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{
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struct scmi_vio_msg *msg = xfer->priv;
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|
|
if (msg) {
|
|
|
|
msg_fetch_response(msg->input, msg->rx_len, xfer);
|
|
|
|
xfer->priv = NULL;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
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);
|
|
|
|
xfer->priv = NULL;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
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,
|
|
|
|
};
|
|
|
|
|
|
|
|
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 */
|
2021-09-16 10:33:36 +00:00
|
|
|
if (scmi_vdev) {
|
|
|
|
dev_err(dev,
|
|
|
|
"One SCMI Virtio device was already initialized: only one allowed.\n");
|
|
|
|
return -EBUSY;
|
|
|
|
}
|
2021-08-03 13:10:24 +00:00
|
|
|
|
|
|
|
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].ready_lock);
|
|
|
|
INIT_LIST_HEAD(&channels[i].free_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_once(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;
|
2021-09-16 10:33:36 +00:00
|
|
|
/* Ensure initialized scmi_vdev is visible */
|
|
|
|
smp_store_mb(scmi_vdev, vdev);
|
2021-08-03 13:10:24 +00:00
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
static void scmi_vio_remove(struct virtio_device *vdev)
|
|
|
|
{
|
2021-09-16 10:33:35 +00:00
|
|
|
/*
|
|
|
|
* 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.
|
|
|
|
*/
|
2021-08-03 13:10:24 +00:00
|
|
|
vdev->config->reset(vdev);
|
|
|
|
vdev->config->del_vqs(vdev);
|
2021-09-16 10:33:36 +00:00
|
|
|
/* Ensure scmi_vdev is visible as NULL */
|
|
|
|
smp_store_mb(scmi_vdev, NULL);
|
2021-08-03 13:10:24 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
static int scmi_vio_validate(struct virtio_device *vdev)
|
|
|
|
{
|
|
|
|
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;
|
|
|
|
}
|
|
|
|
|
|
|
|
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);
|
|
|
|
}
|
|
|
|
|
2021-09-20 10:02:52 +00:00
|
|
|
static void virtio_scmi_exit(void)
|
2021-08-03 13:10:24 +00:00
|
|
|
{
|
|
|
|
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,
|
|
|
|
.max_rx_timeout_ms = 60000, /* for non-realtime virtio devices */
|
|
|
|
.max_msg = 0, /* overridden by virtio_get_max_msg() */
|
|
|
|
.max_msg_size = VIRTIO_SCMI_MAX_MSG_SIZE,
|
|
|
|
};
|