linux-kernel - [PATCH 3.16.y-ckt 115/165] ALSA: hda - Fix regression of HD-audio controller fallback modes

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Message-Id: <1427292138-7021-116-git-send-email-luis.henriques@canonical.com>
Date:	Wed, 25 Mar 2015 14:01:28 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Takashi Iwai <tiwai@...e.de>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 115/165] ALSA: hda - Fix regression of HD-audio controller fallback modes

3.16.7-ckt9 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@...e.de>

commit a1f3f1ca66bd12c339b17a0c2ef93a093f90a277 upstream.

The commit [63e51fd708f5: ALSA: hda - Don't take unresponsive D3
transition too serious] introduced a conditional fallback behavior to
the HD-audio controller depending on the flag set.  However, it
introduced a silly bug, too, that the flag was evaluated in a reverse
way.  This resulted in a regression of HD-audio controller driver
where it can't go to the fallback mode at communication errors.

Unfortunately (or fortunately?) this didn't come up until recently
because the affected code path is an error handling that happens only
on an unstable hardware chip.  Most of recent chips work stably, thus
they didn't hit this problem.  Now, we've got a regression report with
a VIA chip, and this seems indeed requiring the fallback to the
polling mode, and finally the bug was revealed.

The fix is a oneliner to remove the wrong logical NOT in the check.
(Lesson learned - be careful about double negation.)

The bug should be backported to stable, but the patch won't be
applicable to 3.13 or earlier because of the code splits.  The stable
fix patches for earlier kernels will be posted later manually.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=94021
Fixes: 63e51fd708f5 ('ALSA: hda - Don't take unresponsive D3 transition too serious')
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 sound/pci/hda/hda_controller.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/pci/hda/hda_controller.c b/sound/pci/hda/hda_controller.c
index e476a198c15f..c6136597785a 100644
--- a/sound/pci/hda/hda_controller.c
+++ b/sound/pci/hda/hda_controller.c
@@ -1244,7 +1244,7 @@ static unsigned int azx_rirb_get_response(struct hda_bus *bus,
 		}
 	}

-	if (!bus->no_response_fallback)
+	if (bus->no_response_fallback)
 		return -1;

 	if (!chip->polling_mode && chip->poll_count < 2) {
--
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