[PATCH] sound: usb: pcm: fix incorrect power state when playing sound after PM_AUTO suspend

[Macpaul Lin]

This patch fix incorrect power state changed by usb_audio_suspend()
when CONFIG_PM is enabled.

After receiving suspend PM message with auto flag, usb_audio_suspend()
change card's power state to SNDRV_CTL_POWER_D3hot. Only when the other
resume PM message with auto flag can change power state to
SNDRV_CTL_POWER_D0 in __usb_audio_resume().

However, when system is not under auto suspend, resume PM message with
auto flag might not be able to receive on time which cause the power
state was incorrect. At this time, if a player starts to play sound,
will cause snd_usb_pcm_open() to access the card and setup_hw_info() will
resume the card.

But even the card is back to work and all function normal, the power
state is still in SNDRV_CTL_POWER_D3hot. Which cause the infinite loop
happened in snd_power_wait() to check the power state. Thus the
successive setting ioctl cannot be passed to card.

Hence we suggest to change power state to SNDRV_CTL_POWER_D0 when card
has been resumed successfully.

Signed-off-by: Macpaul Lin <macpaul.lin@xxxxxxxxxxxx>
---
 sound/usb/pcm.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index a4e4064..d667ecb 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -1322,6 +1322,17 @@ static int setup_hw_info(struct snd_pcm_runtime *runtime, struct snd_usb_substre
 	if (err < 0)
 		return err;
 
+	/* fix incorrect power state when resuming by open and later ioctls */
+	if (IS_ENABLED(CONFIG_PM) &&
+		snd_power_get_state(subs->stream->chip->card)
+			== SNDRV_CTL_POWER_D3hot) {
+		/* set these variables for power state correction */
+		subs->stream->chip->autosuspended = 0;
+		subs->stream->chip->num_suspended_intf = 1;
+		dev_info(&subs->dev->dev,
+			"change power state from D3hot to D0\n");
+	}
+
 	return snd_usb_autoresume(subs->stream->chip);
 }
 
-- 
1.7.9.5