[PATCH] ALSA: usb-audio: Complete cleanup after system-resume errors

[Will Porter]

A failed system resume can leave the card unusable until reboot.
usb_audio_resume() jumps to err_out when snd_usb_pcm_resume() or
snd_usb_mixer_resume() fails. The error path skips the out: block, which
restores D0 and decrements chip->num_suspended_intf.

The card stays in SNDRV_CTL_POWER_D3hot, so later control access blocks in
snd_power_ref_and_wait(). USB core logs an interface resume callback error.
It does not retry that callback, so a later callback cannot complete the
skipped cleanup.

usb_audio_suspend() increments num_suspended_intf before returning success.
A system-resume callback must consume the system-suspend count even if a
component resume fails. Otherwise, the stranded count skews later suspend
and resume cycles.

Do not apply this cleanup to runtime-resume errors. Runtime PM can retry
-EAGAIN or -EBUSY without another suspend callback. The count must continue
to describe that suspended interface. Other runtime-resume errors latch
runtime_error in the PM core and do not cause an immediate callback retry.

Both parts of the system-resume error path are longstanding. Commit
88a8516a2128a ("ALSA: usbaudio: implement USB autosuspend") introduced
err_out past the D0 restore. Commit 862b2509d157c ("ALSA: usb-audio: Fix
inconsistent card PM state after resume") later moved
num_suspended_intf-- into the out: block. The error path now skips both
operations.

No third-party code is needed to reach the error path.
snd_usb_mixer_resume() ends in snd_usb_mixer_activate(), which returns the
result of usb_submit_urb() for devices that have a mixer status URB. Its
mixer->private_resume hook can also fail through scarlett2_init_notify().
snd_usb_pcm_resume() issues a SET_CUR request to a UAC3 power domain. It
can return -EPIPE or -EIO when the device stalls the request.

Route a component error through out: only when system_suspend is nonzero.
Continue to return runtime-resume errors through err_out. Later component
resume stages remain skipped. The original error still reaches USB core.
A later transfer can fail if the device did not recover.

I reproduced the system-resume failure on an Audient iD14 MkI with an
out-of-tree diagnostic mixer resume hook. An injected -EIO on the unpatched
core left control readers in uninterruptible sleep in
snd_power_ref_and_wait() until a reboot. With this patch, the same failure
restored control access. A second system suspend and resume also succeeded
after I disabled fault injection.

Assisted-by: Claude:claude-opus-5
Assisted-by: Antigravity:gemini-3.1-pro-high
Assisted-by: Codex:gpt-5.6-sol
Fixes: 88a8516a2128a ("ALSA: usbaudio: implement USB autosuspend")
Fixes: 862b2509d157c ("ALSA: usb-audio: Fix inconsistent card PM state after resume")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Will Porter <mrwillporter@xxxxxxxxx>
---
 sound/usb/card.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 24112e491779..9307da95efbe 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -1282,8 +1282,11 @@ static int usb_audio_resume(struct usb_interface *intf)
 
 	list_for_each_entry(as, &chip->pcm_list, list) {
 		err = snd_usb_pcm_resume(as);
-		if (err < 0)
-			goto err_out;
+		if (err < 0) {
+			if (!chip->system_suspend)
+				goto err_out;
+			goto out;
+		}
 	}
 
 	/*
@@ -1292,8 +1295,11 @@ static int usb_audio_resume(struct usb_interface *intf)
 	 */
 	list_for_each_entry(mixer, &chip->mixer_list, list) {
 		err = snd_usb_mixer_resume(mixer);
-		if (err < 0)
-			goto err_out;
+		if (err < 0) {
+			if (!chip->system_suspend)
+				goto err_out;
+			goto out;
+		}
 	}
 
 	list_for_each(p, &chip->midi_list) {

base-commit: e72d5659a2606056a0c34af212b46a3275a55bbf