ALSA: virtio: introduce device suspend/resume support

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

Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
Link: https://lore.kernel.org/r/20210302164709.3142702-10-anton.yakovlev@opensynergy.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/virtio/virtio_card.c

@@ -362,6 +362,58 @@ static void virtsnd_remove(struct virtio_device *vdev)
 	kfree(snd->event_msgs);
 }
 
+#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;
+	unsigned int i;
+
+	virtsnd_disable_event_vq(snd);
+	virtsnd_ctl_msg_cancel_all(snd);
+
+	vdev->config->del_vqs(vdev);
+	vdev->config->reset(vdev);
+
+	for (i = 0; i < snd->nsubstreams; ++i)
+		cancel_work_sync(&snd->substreams[i].elapsed_period);
+
+	kfree(snd->event_msgs);
+	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 },
@@ -374,6 +426,10 @@ static struct virtio_driver virtsnd_driver = {
 	.validate = virtsnd_validate,
 	.probe = virtsnd_probe,
 	.remove = virtsnd_remove,
+#ifdef CONFIG_PM_SLEEP
+	.freeze = virtsnd_freeze,
+	.restore = virtsnd_restore,
+#endif
 };
 
 static int __init init(void)

sound/virtio/virtio_pcm.h

@@ -31,6 +31,8 @@ struct virtio_pcm_msg;
  * @xfer_xrun: Data underflow/overflow state (0 - no xrun, 1 - xrun).
  * @stopped: True if the substream is stopped and must be released on the device
  *           side.
+ * @suspended: True if the substream is suspended and must be reconfigured on
+ *             the device side at resume.
  * @msgs: Allocated I/O messages.
  * @nmsgs: Number of allocated I/O messages.
  * @msg_last_enqueued: Index of the last I/O message added to the virtqueue.
@@ -52,6 +54,7 @@ struct virtio_pcm_substream {
 	bool xfer_enabled;
 	bool xfer_xrun;
 	bool stopped;
+	bool suspended;
 	struct virtio_pcm_msg **msgs;
 	unsigned int nmsgs;
 	int msg_last_enqueued;

sound/virtio/virtio_pcm_ops.c

@@ -115,6 +115,7 @@ static int virtsnd_pcm_open(struct snd_pcm_substream *substream)
 				      SNDRV_PCM_HW_PARAM_PERIODS);
 
 	vss->stopped = !!virtsnd_pcm_msg_pending_num(vss);
+	vss->suspended = false;
 
 	/*
 	 * If the substream has already been used, then the I/O queue may be in
@@ -272,6 +273,7 @@ static int virtsnd_pcm_prepare(struct snd_pcm_substream *substream)
 	struct virtio_device *vdev = vss->snd->vdev;
 	struct virtio_snd_msg *msg;
 
+	if (!vss->suspended) {
 		if (virtsnd_pcm_msg_pending_num(vss)) {
 			dev_err(&vdev->dev, "SID %u: invalid I/O queue state\n",
 				vss->sid);
@@ -280,8 +282,22 @@ static int virtsnd_pcm_prepare(struct snd_pcm_substream *substream)
 
 		vss->buffer_bytes = snd_pcm_lib_buffer_bytes(substream);
 		vss->hw_ptr = 0;
-	vss->xfer_xrun = false;
 		vss->msg_last_enqueued = -1;
+	} else {
+		struct snd_pcm_runtime *runtime = substream->runtime;
+		unsigned int buffer_bytes = snd_pcm_lib_buffer_bytes(substream);
+		unsigned int period_bytes = snd_pcm_lib_period_bytes(substream);
+		int rc;
+
+		rc = virtsnd_pcm_dev_set_params(vss, buffer_bytes, period_bytes,
+						runtime->channels,
+						runtime->format, runtime->rate);
+		if (rc)
+			return rc;
+	}
+
+	vss->xfer_xrun = false;
+	vss->suspended = false;
 	vss->msg_count = 0;
 
 	msg = virtsnd_pcm_ctl_msg_alloc(vss, VIRTIO_SND_R_PCM_PREPARE,
@@ -336,6 +352,9 @@ 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:
+		vss->suspended = true;
+		fallthrough;
 	case SNDRV_PCM_TRIGGER_STOP:
 		vss->stopped = true;
 		fallthrough;