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firmware: arm_scmi: Simplify spinlocks in virtio transport

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Remove unneeded nested irqsave/irqrestore spinlocks.
Add also a few descriptive comments to explain better the system behaviour
at shutdown time.

Link: https://lore.kernel.org/r/20210916103336.7243-2-cristian.marussi@arm.com
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
This commit is contained in:
Cristian Marussi 2021-09-16 11:33:35 +01:00 committed by Sudeep Holla
parent 1cd73200da
commit a14a14595d
1 changed files with 21 additions and 8 deletions
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29
drivers/firmware/arm_scmi/virtio.c
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@ -110,18 +110,16 @@ static void scmi_finalize_message(struct scmi_vio_channel *vioch,
if (vioch->is_rx) { if (vioch->is_rx) {
scmi_vio_feed_vq_rx(vioch, msg); scmi_vio_feed_vq_rx(vioch, msg);
} else { } else {
unsigned long flags; /* Here IRQs are assumed to be already disabled by the caller */
spin_lock(&vioch->lock);
spin_lock_irqsave(&vioch->lock, flags);
list_add(&msg->list, &vioch->free_list); list_add(&msg->list, &vioch->free_list);
spin_unlock_irqrestore(&vioch->lock, flags); spin_unlock(&vioch->lock);
} }
} }
static void scmi_vio_complete_cb(struct virtqueue *vqueue) static void scmi_vio_complete_cb(struct virtqueue *vqueue)
{ {
unsigned long ready_flags; unsigned long ready_flags;
unsigned long flags;
unsigned int length; unsigned int length;
struct scmi_vio_channel *vioch; struct scmi_vio_channel *vioch;
struct scmi_vio_msg *msg; struct scmi_vio_msg *msg;
@ -140,7 +138,8 @@ static void scmi_vio_complete_cb(struct virtqueue *vqueue)
goto unlock_ready_out; goto unlock_ready_out;
} }
spin_lock_irqsave(&vioch->lock, flags); /* IRQs already disabled here no need to irqsave */
spin_lock(&vioch->lock);
if (cb_enabled) { if (cb_enabled) {
virtqueue_disable_cb(vqueue); virtqueue_disable_cb(vqueue);
cb_enabled = false; cb_enabled = false;
@ -151,7 +150,7 @@ static void scmi_vio_complete_cb(struct virtqueue *vqueue)
goto unlock_out; goto unlock_out;
cb_enabled = true; cb_enabled = true;
} }
spin_unlock_irqrestore(&vioch->lock, flags); spin_unlock(&vioch->lock);
if (msg) { if (msg) {
msg->rx_len = length; msg->rx_len = length;
@ -161,11 +160,18 @@ static void scmi_vio_complete_cb(struct virtqueue *vqueue)
scmi_finalize_message(vioch, msg); scmi_finalize_message(vioch, msg);
} }
/*
* Release ready_lock and re-enable IRQs between loop iterations
* to allow virtio_chan_free() to possibly kick in and set the
* flag vioch->ready to false even in between processing of
* messages, so as to force outstanding messages to be ignored
* when system is shutting down.
*/
spin_unlock_irqrestore(&vioch->ready_lock, ready_flags); spin_unlock_irqrestore(&vioch->ready_lock, ready_flags);
} }
unlock_out: unlock_out:
spin_unlock_irqrestore(&vioch->lock, flags); spin_unlock(&vioch->lock);
unlock_ready_out: unlock_ready_out:
spin_unlock_irqrestore(&vioch->ready_lock, ready_flags); spin_unlock_irqrestore(&vioch->ready_lock, ready_flags);
} }
@ -435,6 +441,13 @@ static int scmi_vio_probe(struct virtio_device *vdev)
static void scmi_vio_remove(struct virtio_device *vdev) 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.
*/
vdev->config->reset(vdev); vdev->config->reset(vdev);
vdev->config->del_vqs(vdev); vdev->config->del_vqs(vdev);
scmi_vdev = NULL; scmi_vdev = NULL;