On Wed, 2020-06-03 at 17:37 +0200, Takashi Iwai wrote:
When a USB-audio interface gets runtime-suspended via auto-pm feature, the driver suspends all functionality and increment chip->num_suspended_intf. Later on, when the system gets suspended to S3, the driver increments chip->num_suspended_intf again, skips the device changes, and sets the card power state to SNDRV_CTL_POWER_D3hot. In return, when the system gets resumed from S3, the resume callback decrements chip->num_suspended_intf. Since this refcount is still not zero (it's been runtime-suspended), the whole resume is skipped. But there is a small pitfall here.
The problem is that the driver doesn't restore the card power state after this resume call, leaving it as SNDRV_CTL_POWER_D3hot. So, even after the system resume finishes, the card instance still appears as if it were system-suspended, and this confuses many ioctl accesses that are blocked unexpectedly.
In details, we have two issues behind the scene: one is that the card power state is changed only when the refcount becomes zero, and another is that the prior auto-suspend check is kept in a boolean flag. Although the latter problem is almost negligible since the auto-pm feature is imposed only on the primary interface, but this can be a potential problem on the devices with multiple interfaces.
This patch addresses those issues by the following:
Replace chip->autosuspended boolean flag with chip->system_suspend counter
At the first system-suspend, chip->num_suspended_intf is recorded to chip->system_suspend
At system-resume, the card power state is restored when the chip->num_suspended_intf refcount reaches to chip->system_suspend, i.e. the state returns to the auto-suspended
Also, the patch fixes yet another hidden problem by the code refactoring along with the fixes above: namely, when some resume procedure failed, the driver left chip->num_suspended_intf that was already decreased, and it might lead to the refcount unbalance. In the new code, the refcount decrement is done after the whole resume procedure, and the problem is avoided as well.
Fixes: 0662292aec05 ("ALSA: usb-audio: Handle normal and auto-suspend equally") Reported-and-tested-by: Macpaul Lin macpaul.lin@mediatek.com Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de
sound/usb/card.c | 19 ++++++++++++------- sound/usb/usbaudio.h | 2 +- 2 files changed, 13 insertions(+), 8 deletions(-)
diff --git a/sound/usb/card.c b/sound/usb/card.c index fd6fd1726ea0..359f7a04be1c 100644 --- a/sound/usb/card.c +++ b/sound/usb/card.c @@ -843,9 +843,6 @@ static int usb_audio_suspend(struct usb_interface *intf, pm_message_t message) if (chip == (void *)-1L) return 0;
- chip->autosuspended = !!PMSG_IS_AUTO(message);
- if (!chip->autosuspended)
snd_power_change_state(chip->card, SNDRV_CTL_POWER_D3hot);@@ -858,6 +855,11 @@ static int usb_audio_suspend(struct usb_interface *intf, pm_message_t message) snd_usb_mixer_suspend(mixer); }
- if (!PMSG_IS_AUTO(message) && !chip->system_suspend) {
snd_power_change_state(chip->card, SNDRV_CTL_POWER_D3hot);chip->system_suspend = chip->num_suspended_intf;- }
- return 0;
}
@@ -871,10 +873,10 @@ static int __usb_audio_resume(struct usb_interface *intf, bool reset_resume)
if (chip == (void *)-1L) return 0;
if (--chip->num_suspended_intf)
return 0;atomic_inc(&chip->active); /* avoid autopm */
if (chip->num_suspended_intf > 1)
goto out;list_for_each_entry(as, &chip->pcm_list, list) { err = snd_usb_pcm_resume(as);
@@ -896,9 +898,12 @@ static int __usb_audio_resume(struct usb_interface *intf, bool reset_resume) snd_usbmidi_resume(p); }
- if (!chip->autosuspended)
- out:
- if (chip->num_suspended_intf == chip->system_suspend) { snd_power_change_state(chip->card, SNDRV_CTL_POWER_D0);
- chip->autosuspended = 0;
chip->system_suspend = 0;- }
- chip->num_suspended_intf--;
err_out: atomic_dec(&chip->active); /* allow autopm after this point */ diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h index 1c892c7f14d7..e0ebfb25fbd5 100644 --- a/sound/usb/usbaudio.h +++ b/sound/usb/usbaudio.h @@ -26,7 +26,7 @@ struct snd_usb_audio { struct usb_interface *pm_intf; u32 usb_id; struct mutex mutex;
- unsigned int autosuspended:1;
- unsigned int system_suspend; atomic_t active; atomic_t shutdown; atomic_t usage_count;
Tested-by: Macpaul Lin macpaul.lin@mediatek.com