[PATCH v4 9/9] ALSA: virtio: introduce device suspend/resume support

[Anton Yakovlev]

All running PCM substreams are stopped on device suspend and restarted
on device resume.

Signed-off-by: Anton Yakovlev <anton.yakovlev@xxxxxxxxxxxxxxx>
---
 sound/virtio/virtio_card.c    | 57 +++++++++++++++++++++++++++++++++++
 sound/virtio/virtio_pcm.c     |  1 +
 sound/virtio/virtio_pcm_ops.c | 44 ++++++++++++++++++++-------
 3 files changed, 91 insertions(+), 11 deletions(-)

diff --git a/sound/virtio/virtio_card.c b/sound/virtio/virtio_card.c
index 787a4dec1da8..1f0a0fa7bbc0 100644
--- a/sound/virtio/virtio_card.c
+++ b/sound/virtio/virtio_card.c
@@ -373,6 +373,59 @@ static void virtsnd_config_changed(struct virtio_device *vdev)
 			 "sound device configuration was changed\n");
 }
 
+#ifdef CONFIG_PM_SLEEP
+/**
+ * virtsnd_freeze() - Suspend device.
+ * @vdev: VirtIO parent device.
+ *
+ * Context: Any context.
+ * Return: 0 on success, -errno on failure.
+ */
+static int virtsnd_freeze(struct virtio_device *vdev)
+{
+	struct virtio_snd *snd = vdev->priv;
+
+	/* Stop all the virtqueues. */
+	vdev->config->reset(vdev);
+	vdev->config->del_vqs(vdev);
+
+	virtsnd_ctl_msg_cancel_all(snd);
+
+	kfree(snd->event_msgs);
+
+	/*
+	 * If the virtsnd_restore() fails before re-allocating events, then we
+	 * get a dangling pointer here.
+	 */
+	snd->event_msgs = NULL;
+
+	return 0;
+}
+
+/**
+ * virtsnd_restore() - Resume device.
+ * @vdev: VirtIO parent device.
+ *
+ * Context: Any context.
+ * Return: 0 on success, -errno on failure.
+ */
+static int virtsnd_restore(struct virtio_device *vdev)
+{
+	struct virtio_snd *snd = vdev->priv;
+	int rc;
+
+	rc = virtsnd_find_vqs(snd);
+	if (rc)
+		return rc;
+
+	virtio_device_ready(vdev);
+
+	virtsnd_enable_event_vq(snd);
+
+	return 0;
+}
+#endif /* CONFIG_PM_SLEEP */
+
 static const struct virtio_device_id id_table[] = {
 	{ VIRTIO_ID_SOUND, VIRTIO_DEV_ANY_ID },
 	{ 0 },
@@ -386,6 +439,10 @@ static struct virtio_driver virtsnd_driver = {
 	.probe = virtsnd_probe,
 	.remove = virtsnd_remove,
 	.config_changed = virtsnd_config_changed,
+#ifdef CONFIG_PM_SLEEP
+	.freeze = virtsnd_freeze,
+	.restore = virtsnd_restore,
+#endif
 };
 
 static int __init init(void)
diff --git a/sound/virtio/virtio_pcm.c b/sound/virtio/virtio_pcm.c
index 5f7b4090c6a2..d7471e0a9d04 100644
--- a/sound/virtio/virtio_pcm.c
+++ b/sound/virtio/virtio_pcm.c
@@ -109,6 +109,7 @@ static int virtsnd_pcm_build_hw(struct virtio_pcm_substream *vss,
 		SNDRV_PCM_INFO_BATCH |
 		SNDRV_PCM_INFO_BLOCK_TRANSFER |
 		SNDRV_PCM_INFO_INTERLEAVED |
+		SNDRV_PCM_INFO_RESUME |
 		SNDRV_PCM_INFO_PAUSE;
 
 	if (!info->channels_min || info->channels_min > info->channels_max) {
diff --git a/sound/virtio/virtio_pcm_ops.c b/sound/virtio/virtio_pcm_ops.c
index 07510778b555..ccef64502c13 100644
--- a/sound/virtio/virtio_pcm_ops.c
+++ b/sound/virtio/virtio_pcm_ops.c
@@ -218,6 +218,10 @@ static int virtsnd_pcm_hw_params(struct snd_pcm_substream *substream,
 	if (rc)
 		return rc;
 
+	/* If messages have already been allocated before, do nothing. */
+	if (runtime->status->state == SNDRV_PCM_STATE_SUSPENDED)
+		return 0;
+
 	return virtsnd_pcm_msg_alloc(vss, periods, period_bytes);
 }
 
@@ -258,19 +262,21 @@ static int virtsnd_pcm_prepare(struct snd_pcm_substream *substream)
 	}
 
 	spin_lock_irqsave(&vss->lock, flags);
-	/*
-	 * Since I/O messages are asynchronous, they can be completed
-	 * when the runtime structure no longer exists. Since each
-	 * completion implies incrementing the hw_ptr, we cache all the
-	 * current values needed to compute the new hw_ptr value.
-	 */
-	vss->frame_bytes = runtime->frame_bits >> 3;
-	vss->period_size = runtime->period_size;
-	vss->buffer_size = runtime->buffer_size;
+	if (runtime->status->state != SNDRV_PCM_STATE_SUSPENDED) {
+		/*
+		 * Since I/O messages are asynchronous, they can be completed
+		 * when the runtime structure no longer exists. Since each
+		 * completion implies incrementing the hw_ptr, we cache all the
+		 * current values needed to compute the new hw_ptr value.
+		 */
+		vss->frame_bytes = runtime->frame_bits >> 3;
+		vss->period_size = runtime->period_size;
+		vss->buffer_size = runtime->buffer_size;
 
-	vss->hw_ptr = 0;
+		vss->hw_ptr = 0;
+		vss->msg_last_enqueued = -1;
+	}
 	vss->xfer_xrun = false;
-	vss->msg_last_enqueued = -1;
 	vss->msg_count = 0;
 	spin_unlock_irqrestore(&vss->lock, flags);
 
@@ -300,6 +306,21 @@ static int virtsnd_pcm_trigger(struct snd_pcm_substream *substream, int command)
 	int rc;
 
 	switch (command) {
+	case SNDRV_PCM_TRIGGER_RESUME: {
+		/*
+		 * We restart the substream by executing the standard command
+		 * sequence.
+		 */
+		rc = virtsnd_pcm_hw_params(substream, NULL);
+		if (rc)
+			return rc;
+
+		rc = virtsnd_pcm_prepare(substream);
+		if (rc)
+			return rc;
+
+		fallthrough;
+	}
 	case SNDRV_PCM_TRIGGER_START:
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE: {
 		struct virtio_snd_queue *queue = virtsnd_pcm_queue(vss);
@@ -326,6 +347,7 @@ static int virtsnd_pcm_trigger(struct snd_pcm_substream *substream, int command)
 
 		return virtsnd_ctl_msg_send_sync(snd, msg);
 	}
+	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_STOP:
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH: {
 		spin_lock_irqsave(&vss->lock, flags);
-- 
2.30.0