Patch "ALSA: hda - Don't trust the reported actual power state" has been added to the 4.5-stable tree

This is a note to let you know that I've just added the patch titled

ALSA: hda - Don't trust the reported actual power state

to the 4.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
alsa-hda-don-t-trust-the-reported-actual-power-state.patch
and it can be found in the queue-4.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Takashi Iwai <[email protected]>
Date: Sun, 17 Apr 2016 09:39:41 +0200
Subject: ALSA: hda - Don't trust the reported actual power state

From: Takashi Iwai <[email protected]>

commit 50fd4987c4f3c3ebf0ce94d932732011bbdc7c71 upstream.

We've got a regression report that the recording on Mac with a cirrus codec doesn't work any longer. This turned out to be the missing power up to D0 by power_save_node enablement.

After analyzing the traces, we found out that the culprit is that the codec advertises the "actual" power state of a few nodes to be D0 while the "target" power state is D3. This inconsistency is usually OK, as it implies the power transition. But in the case of cirrus codec, this seems to be stuck to D3 while it's not actually D0.

This patch addresses the issue by checking the power state difference more strictly. It sends the power-state change verb unless both the target and the actual power states show the given value.

We may introduce yet another flag indicating the possible broken hardware power state, but it's anyway safer to set the proper power state even in a transition (at least it's harmless as long as the target state is same). So this simpler change was applied now.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=116171

---
 sound/pci/hda/hda_generic.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

@@ -826,7 +826,7 @@ static hda_nid_t path_power_update(struc
 				   bool allow_powerdown)
 {
 	hda_nid_t nid, changed = 0;
-	int i, state;
+	int i, state, power;
 
 	for (i = 0; i < path->depth; i++) {
 		nid = path->path[i];

@@ -838,7 +838,9 @@ static hda_nid_t path_power_update(struc
 			state = AC_PWRST_D0;
 		else
 			state = AC_PWRST_D3;
-		if (!snd_hda_check_power_state(codec, nid, state)) {
+		power = snd_hda_codec_read(codec, nid, 0,
+					   AC_VERB_GET_POWER_STATE, 0);
+		if (power != (state | (state << 4))) {
 			snd_hda_codec_write(codec, nid, 0,
 					    AC_VERB_SET_POWER_STATE, state);
 			changed = nid;

Patches currently in stable-queue which might be from [email protected] are

queue-4.5/alsa-pcxhr-fix-missing-mutex-unlock.patch queue-4.5/alsa-hda-add-dock-support-for-thinkpad-x260.patch queue-4.5/alsa-hda-keep-powering-up-adcs-on-cirrus-codecs.patch queue-4.5/alsa-hda-update-bclk-also-at-hotplug-for-i915-hsw-bdw.patch queue-4.5/alsa-hda-add-pci-id-for-intel-broxton-t.patch queue-4.5/alsa-hda-don-t-trust-the-reported-actual-power-state.patch queue-4.5/alsa-hda-realtek-add-alc3234-headset-mode-for-optiplex-9020m.patch