[RFC PATCH] ALSA: hda/hdmi: fix race in handling acomp ELD notification at resume

[Kai Vehmanen]

When snd-hda-codec-hdmi is used with ASoC HDA controller like SOF (acomp
used for ELD notifications), display connection change done during suspend,
can be lost due to following sequence of events:

  1. system in S3 suspend
  2. DP/HDMI receiver connected
  3. system resumed
  4. HDA controller resumed, but card->deferred_resume_work not complete
  5. acomp eld_notify callback
  6. eld_notify ignored as power state is not CTL_POWER_D0
  7. HDA resume deferred work completed, power state set to CTL_POWER_D0

This results in losing the notification, and the jack state reported to
user-space is not correct.

The check on step 6 was added in commit 8ae743e82f0b ("ALSA: hda - Skip
ELD notification during system suspend"). It would seem with the deferred
resume logic in ASoC core, this check is not safe.

Fix the issue by modifying the check to only skip ELD notification
processing if power state is D3 or deeper. This helps in the ASoC
controller case as card power state is set to D2 at start of
soc_resume_deferred().

BugLink: https://github.com/thesofproject/linux/issues/2825
Signed-off-by: Kai Vehmanen <kai.vehmanen at linux.intel.com>
---
 sound/pci/hda/patch_hdmi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

NOTES:
 - I wonder if there is a better way to check for system suspend
   case than looking at snd_power_get_state()
 - 'chip->pm_prepared' is one option, but this is not directly available
   to codec drivers
 - storing PM target is hda_codec_pm_prepare() is perhaps one option

diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
index 5de3666a7101..a43df036db1d 100644
--- a/sound/pci/hda/patch_hdmi.c
+++ b/sound/pci/hda/patch_hdmi.c
@@ -2654,7 +2654,7 @@ static void generic_acomp_pin_eld_notify(void *audio_ptr, int port, int dev_id)
 	/* skip notification during system suspend (but not in runtime PM);
 	 * the state will be updated at resume
 	 */
-	if (snd_power_get_state(codec->card) != SNDRV_CTL_POWER_D0)
+	if (snd_power_get_state(codec->card) >= SNDRV_CTL_POWER_D3)
 		return;
 	/* ditto during suspend/resume process itself */
 	if (snd_hdac_is_in_pm(&codec->core))
@@ -2840,7 +2840,7 @@ static void intel_pin_eld_notify(void *audio_ptr, int port, int pipe)
 	/* skip notification during system suspend (but not in runtime PM);
 	 * the state will be updated at resume
 	 */
-	if (snd_power_get_state(codec->card) != SNDRV_CTL_POWER_D0)
+	if (snd_power_get_state(codec->card) >= SNDRV_CTL_POWER_D3)
 		return;
 	/* ditto during suspend/resume process itself */
 	if (snd_hdac_is_in_pm(&codec->core))

base-commit: 7dc53a38e4ac00d68943bab91deadc67f07d4a0b
-- 
2.31.0