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509 lines
13 KiB
509 lines
13 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) 2020-2021 OpenSynergy. |
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* Copyright (C) 2021 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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#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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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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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_once(vioch->cinfo->dev, |
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"failed to add to 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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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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/* Here IRQs are assumed to be already disabled by the caller */ |
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spin_lock(&vioch->lock); |
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list_add(&msg->list, &vioch->free_list); |
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spin_unlock(&vioch->lock); |
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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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/* IRQs already disabled here no need to irqsave */ |
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spin_lock(&vioch->lock); |
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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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spin_unlock(&vioch->lock); |
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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 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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spin_unlock_irqrestore(&vioch->ready_lock, ready_flags); |
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} |
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unlock_out: |
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spin_unlock(&vioch->lock); |
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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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return vioch && !vioch->cinfo; |
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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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scmi_vio_feed_vq_rx(vioch, msg); |
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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) { |
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msg_fetch_response(msg->input, msg->rx_len, xfer); |
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xfer->priv = NULL; |
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} |
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} |
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static void virtio_fetch_notification(struct scmi_chan_info *cinfo, |
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size_t max_len, 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) { |
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msg_fetch_notification(msg->input, msg->rx_len, max_len, xfer); |
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xfer->priv = NULL; |
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} |
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} |
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static const struct scmi_transport_ops scmi_virtio_ops = { |
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.link_supplier = virtio_link_supplier, |
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.chan_available = virtio_chan_available, |
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.chan_setup = virtio_chan_setup, |
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.chan_free = virtio_chan_free, |
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.get_max_msg = virtio_get_max_msg, |
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.send_message = virtio_send_message, |
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.fetch_response = virtio_fetch_response, |
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.fetch_notification = virtio_fetch_notification, |
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}; |
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static int scmi_vio_probe(struct virtio_device *vdev) |
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{ |
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struct device *dev = &vdev->dev; |
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struct scmi_vio_channel *channels; |
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bool have_vq_rx; |
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int vq_cnt; |
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int i; |
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int ret; |
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struct virtqueue *vqs[VIRTIO_SCMI_VQ_MAX_CNT]; |
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/* Only one SCMI VirtiO device allowed */ |
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if (scmi_vdev) { |
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dev_err(dev, |
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"One SCMI Virtio device was already initialized: only one allowed.\n"); |
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return -EBUSY; |
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} |
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have_vq_rx = scmi_vio_have_vq_rx(vdev); |
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vq_cnt = have_vq_rx ? VIRTIO_SCMI_VQ_MAX_CNT : 1; |
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channels = devm_kcalloc(dev, vq_cnt, sizeof(*channels), GFP_KERNEL); |
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if (!channels) |
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return -ENOMEM; |
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if (have_vq_rx) |
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channels[VIRTIO_SCMI_VQ_RX].is_rx = true; |
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ret = virtio_find_vqs(vdev, vq_cnt, vqs, scmi_vio_complete_callbacks, |
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scmi_vio_vqueue_names, NULL); |
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if (ret) { |
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dev_err(dev, "Failed to get %d virtqueue(s)\n", vq_cnt); |
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return ret; |
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} |
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for (i = 0; i < vq_cnt; i++) { |
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unsigned int sz; |
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spin_lock_init(&channels[i].lock); |
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spin_lock_init(&channels[i].ready_lock); |
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INIT_LIST_HEAD(&channels[i].free_list); |
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channels[i].vqueue = vqs[i]; |
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sz = virtqueue_get_vring_size(channels[i].vqueue); |
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/* Tx messages need multiple descriptors. */ |
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if (!channels[i].is_rx) |
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sz /= DESCRIPTORS_PER_TX_MSG; |
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if (sz > MSG_TOKEN_MAX) { |
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dev_info_once(dev, |
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"%s virtqueue could hold %d messages. Only %ld allowed to be pending.\n", |
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channels[i].is_rx ? "rx" : "tx", |
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sz, MSG_TOKEN_MAX); |
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sz = MSG_TOKEN_MAX; |
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} |
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channels[i].max_msg = sz; |
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} |
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vdev->priv = channels; |
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/* Ensure initialized scmi_vdev is visible */ |
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smp_store_mb(scmi_vdev, vdev); |
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return 0; |
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} |
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static void scmi_vio_remove(struct virtio_device *vdev) |
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{ |
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/* |
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* Once we get here, virtio_chan_free() will have already been called by |
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* the SCMI core for any existing channel and, as a consequence, all the |
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* virtio channels will have been already marked NOT ready, causing any |
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* outstanding message on any vqueue to be ignored by complete_cb: now |
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* we can just stop processing buffers and destroy the vqueues. |
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*/ |
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vdev->config->reset(vdev); |
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vdev->config->del_vqs(vdev); |
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/* Ensure scmi_vdev is visible as NULL */ |
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smp_store_mb(scmi_vdev, NULL); |
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} |
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static int scmi_vio_validate(struct virtio_device *vdev) |
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{ |
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if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) { |
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dev_err(&vdev->dev, |
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"device does not comply with spec version 1.x\n"); |
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return -EINVAL; |
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} |
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return 0; |
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} |
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static unsigned int features[] = { |
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VIRTIO_SCMI_F_P2A_CHANNELS, |
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}; |
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static const struct virtio_device_id id_table[] = { |
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{ VIRTIO_ID_SCMI, VIRTIO_DEV_ANY_ID }, |
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{ 0 } |
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}; |
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static struct virtio_driver virtio_scmi_driver = { |
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.driver.name = "scmi-virtio", |
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.driver.owner = THIS_MODULE, |
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.feature_table = features, |
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.feature_table_size = ARRAY_SIZE(features), |
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.id_table = id_table, |
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.probe = scmi_vio_probe, |
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.remove = scmi_vio_remove, |
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.validate = scmi_vio_validate, |
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}; |
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static int __init virtio_scmi_init(void) |
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{ |
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return register_virtio_driver(&virtio_scmi_driver); |
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} |
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static void virtio_scmi_exit(void) |
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{ |
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unregister_virtio_driver(&virtio_scmi_driver); |
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} |
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const struct scmi_desc scmi_virtio_desc = { |
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.transport_init = virtio_scmi_init, |
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.transport_exit = virtio_scmi_exit, |
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.ops = &scmi_virtio_ops, |
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.max_rx_timeout_ms = 60000, /* for non-realtime virtio devices */ |
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.max_msg = 0, /* overridden by virtio_get_max_msg() */ |
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.max_msg_size = VIRTIO_SCMI_MAX_MSG_SIZE, |
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};
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