[RFC PATCH v6 5/8] ALSA: usb: babyfacepro: add S3 suspend/resume

["Ismaïl Bahloul" <i.bahloul01@gmail.com>]

The device loses its registers across a system suspend.  On suspend,
let the PCM core suspend the substreams (applications get -ESTRPIPE and
restart), then kill the session's URBs before cancelling the stream
work their handlers queue.  On resume, re-run the cold init and replay
the cached mixer state and flags.

USB autosuspend stays disabled: nothing in the driver holds a PM
reference while streaming.

Co-developed-by: David Fredman <davfre@gmail.com>
Signed-off-by: David Fredman <davfre@gmail.com>
Signed-off-by: Ismaïl Bahloul <i.bahloul01@gmail.com>
---
 sound/usb/babyfacepro/babyfacepro.c | 77 ++++++++++++++++++++++++-----
 sound/usb/babyfacepro/babyfacepro.h |  6 +--
 2 files changed, 69 insertions(+), 14 deletions(-)

diff --git a/sound/usb/babyfacepro/babyfacepro.c b/sound/usb/babyfacepro/babyfacepro.c
index 0678bea58..aaa74ee68 100644
--- a/sound/usb/babyfacepro/babyfacepro.c
+++ b/sound/usb/babyfacepro/babyfacepro.c
@@ -3,8 +3,8 @@
  * RME Babyface Pro / Pro FS - proprietary-mode USB audio driver
  *
  * Core driver: USB vendor requests + cold init, interrupt-URB PCM
- * streaming, mixer-state persistence across re-probes, and the card
- * lifecycle (probe/disconnect/module entry).
+ * streaming, mixer-state persistence across re-probes/resume, and
+ * the card lifecycle (probe/disconnect/PM/module entry).
  *
  * See babyfacepro.h for the shared device state and register map,
  * and babyfacepro-ctl.c for the ALSA control surface.
@@ -200,9 +200,9 @@ int bf_pitch_write(struct snd_usb_babyface *chip, int pitch)
 }
 
 /* The cold-start init (cap_coldplug.pcap), verbatim from the user-space
- * reference (protocol::streaming_init).  Run at probe, where the
- * device state is unknown; a session start does not need it (see
- * babyface_stream_start()).
+ * reference (protocol::streaming_init).  Run at probe and after resume,
+ * where the device state is unknown; a session start does not need it
+ * (see babyface_stream_start()).
  */
 int bf_cold_init(struct snd_usb_babyface *chip)
 {
@@ -280,8 +280,9 @@ int bf_cold_init(struct snd_usb_babyface *chip)
 static LIST_HEAD(bf_saved_list);
 static DEFINE_MUTEX(bf_saved_mutex);
 
-/* Re-apply the whole cached mixer state to the device, whose registers
- * the cold init cleared.  Caller holds chip->mutex.
+/* Re-apply the whole cached mixer state after a resume (the device
+ * lost its registers across a system suspend - TotalMix does the same
+ * re-apply).  Caller holds chip->mutex.
  */
 int babyface_restore_state(struct snd_usb_babyface *chip)
 {
@@ -409,7 +410,7 @@ int bf_state_apply_flags(struct snd_usb_babyface *chip)
 	/* Re-apply an engaged DIM (the fixed -20 dB Phones pair + flag).  The
 	 * level DIM releases back to is not persisted: it always tracks the
 	 * Phones master while DIM is engaged, so rebuild it here - otherwise a
-	 * DIM released after a re-probe would drive Phones to
+	 * DIM released after a re-probe or resume would drive Phones to
 	 * silence (dim_saved still zero on the fresh chip).
 	 */
 	if (chip->dim) {
@@ -979,8 +980,9 @@ static int babyface_stream_start(struct snd_usb_babyface *chip)
 	/* A session start is what the RME Windows driver sends
 	 * (cap_audio): the trigger pair, the URBs, the arm.  The device
 	 * keeps its mixer state between sessions, so nothing is cleared
-	 * or re-applied here; the cold init runs at probe only.  The rate
-	 * is written first: hw_params only re-points the speed multiplier.
+	 * or re-applied here; the cold init runs at probe and resume
+	 * only.  The rate is written first: hw_params only re-points the
+	 * speed multiplier.
 	 */
 	ret = bf_clock_write(chip);
 	if (ret < 0)
@@ -1667,7 +1669,8 @@ static int babyface_probe(struct usb_interface *intf,
 	chip->card = card;
 
 	chip->dev = usb_get_dev(dev);
-	/* USB autosuspend is untested: nothing in this driver holds a PM
+	/* USB autosuspend is untested: babyface_suspend()/_resume() don't
+	 * check PMSG_IS_AUTO, and nothing in this driver holds a PM
 	 * reference while streaming, so an autosuspend request could race
 	 * a live stream.  Disable it explicitly rather than ship an
 	 * untested code path - full autosuspend support (correct
@@ -1925,6 +1928,56 @@ static void babyface_disconnect(struct usb_interface *intf)
 	snd_card_free_when_closed(chip->card);
 }
 
+static int babyface_suspend(struct usb_interface *intf, pm_message_t message)
+{
+	struct snd_usb_babyface *chip = usb_get_intfdata(intf);
+
+	struct snd_device *sdev;
+
+	if (!chip)
+		return 0;
+	list_for_each_entry(sdev, &chip->card->devices, list) {
+		if (sdev->type == SNDRV_DEV_PCM)
+			snd_pcm_suspend_all(sdev->device_data);
+	}
+	/* The URB handlers queue the work: kill them first. */
+	mutex_lock(&chip->mutex);
+	if (chip->streaming)
+		babyface_stream_kill(chip);
+	mutex_unlock(&chip->mutex);
+	cancel_work_sync(&chip->stream_work);
+	return 0;
+}
+
+static int babyface_resume(struct usb_interface *intf)
+{
+	struct snd_usb_babyface *chip = usb_get_intfdata(intf);
+	int err;
+
+	if (!chip)
+		return 0;
+
+	/* The device lost its state across the suspend; re-run the cold
+	 * init and re-apply the cached mixer state.  Suspended PCM
+	 * substreams are woken by the core - apps get -ESTRPIPE and
+	 * restart (prepare starts a new session).
+	 */
+	mutex_lock(&chip->mutex);
+	err = usb_set_interface(chip->dev, BF_IFACE, chip->alt);
+	if (err < 0)
+		goto out;
+	err = bf_cold_init(chip);
+	if (err < 0)
+		goto out;
+	err = babyface_restore_state(chip);
+	if (err < 0)
+		goto out;
+	err = bf_state_apply_flags(chip);
+out:
+	mutex_unlock(&chip->mutex);
+	return err;
+}
+
 static const struct usb_device_id babyface_ids[] = {
 	{ USB_DEVICE(USB_VENDOR_RME, USB_PRODUCT_BABYFACE_PRO_FS) },
 	{ }
@@ -1935,6 +1988,8 @@ static struct usb_driver babyface_driver = {
 	.name = "snd-usb-babyface-pro",
 	.probe = babyface_probe,
 	.disconnect = babyface_disconnect,
+	.suspend = babyface_suspend,
+	.resume = babyface_resume,
 	.id_table = babyface_ids,
 };
 
diff --git a/sound/usb/babyfacepro/babyfacepro.h b/sound/usb/babyfacepro/babyfacepro.h
index 783ea03ac..e324e8411 100644
--- a/sound/usb/babyfacepro/babyfacepro.h
+++ b/sound/usb/babyfacepro/babyfacepro.h
@@ -12,7 +12,7 @@
  * snd-usb-audio quirk.
  *
  * babyfacepro.c holds the card lifecycle, the PCM stream and the
- * mixer-state persistence across re-probes;
+ * mixer-state persistence across re-probes and resume;
  * babyfacepro-ctl.c holds the ALSA control surface - the hardware
  * mixer.
  *
@@ -344,7 +344,7 @@ struct snd_usb_babyface {
 	struct snd_kcontrol *dim_kctl;      /* for snd_ctl_notify */
 };
 
-/* The mixer state cached across interface re-probes (see
+/* The mixer state cached across interface re-probes/resume (see
  * babyfacepro.c's own comment on bf_state_save/bf_state_restore).
  */
 struct bf_saved {
@@ -395,7 +395,7 @@ void babyface_pcm_stop_both(struct snd_usb_babyface *chip, snd_pcm_state_t state
 void babyface_stream_work(struct work_struct *work);
 extern const struct snd_pcm_hw_constraint_list bf_rates_constraint;
 
-/* Mixer-state persistence across interface re-probes. */
+/* Mixer-state persistence across interface re-probes/resume. */
 void bf_state_save(struct snd_usb_babyface *chip);
 int bf_state_restore(struct snd_usb_babyface *chip);
 void bf_state_purge(void);
-- 
2.56.0