[3.5.y.z extended stable] Patch "ASoC: fsl: imx-pcm-fiq: omit fiq counter to avoid harm in unbalanced" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ASoC: fsl: imx-pcm-fiq: omit fiq counter to avoid harm in unbalanced

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From eccd5cb61dbbd5845b8b1dd25aeb05c0c3ff753c Mon Sep 17 00:00:00 2001
From: Oskar Schirmer <oskar at scara.com>
Date: Tue, 12 Nov 2013 15:46:38 +0000
Subject: ASoC: fsl: imx-pcm-fiq: omit fiq counter to avoid harm in unbalanced
 situations

commit fc7dc61d9a87011aaf8a6eb3144ebf9552adf5d2 upstream.

Unbalanced calls to snd_imx_pcm_trigger() may result in endless
FIQ activity and thus provoke eternal sound. While on the first glance,
the switch statement looks pretty symmetric, the SUSPEND/RESUME
pair is not: the suspend case comes along snd_pcm_suspend_all(),
which for fsl/imx-pcm-fiq is called only at snd_soc_suspend(),
but the resume case originates straight from the SNDRV_PCM_IOCTL_RESUME.
This way userland may provoke an unbalanced resume, which might cause
the fiq_enable counter to increase and never return to zero again,
so eventually imx_pcm_fiq is never disabled.

Simply removing the fiq_enable will solve the problem, as long as
one never goes play and capture game simultaneously, but beware
trying both at once, the early TRIGGER_STOP will cut off the other
activity prematurely. So now playing and capturing is scrutinized
separately, instead of by counting.

Signed-off-by: Oskar Schirmer <oskar at scara.com>
Signed-off-by: Mark Brown <broonie at linaro.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 sound/soc/fsl/imx-pcm-fiq.c | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/sound/soc/fsl/imx-pcm-fiq.c b/sound/soc/fsl/imx-pcm-fiq.c
index 456b7d7..b18279d 100644
--- a/sound/soc/fsl/imx-pcm-fiq.c
+++ b/sound/soc/fsl/imx-pcm-fiq.c
@@ -42,7 +42,8 @@ struct imx_pcm_runtime_data {
 	struct hrtimer hrt;
 	int poll_time_ns;
 	struct snd_pcm_substream *substream;
-	atomic_t running;
+	atomic_t playing;
+	atomic_t capturing;
 };

 static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt)
@@ -54,7 +55,7 @@ static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt)
 	struct pt_regs regs;
 	unsigned long delta;

-	if (!atomic_read(&iprtd->running))
+	if (!atomic_read(&iprtd->playing) && !atomic_read(&iprtd->capturing))
 		return HRTIMER_NORESTART;

 	get_fiq_regs(&regs);
@@ -122,7 +123,6 @@ static int snd_imx_pcm_prepare(struct snd_pcm_substream *substream)
 	return 0;
 }

-static int fiq_enable;
 static int imx_pcm_fiq;

 static int snd_imx_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
@@ -134,23 +134,27 @@ static int snd_imx_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
 	case SNDRV_PCM_TRIGGER_START:
 	case SNDRV_PCM_TRIGGER_RESUME:
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
-		atomic_set(&iprtd->running, 1);
+		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+			atomic_set(&iprtd->playing, 1);
+		else
+			atomic_set(&iprtd->capturing, 1);
 		hrtimer_start(&iprtd->hrt, ns_to_ktime(iprtd->poll_time_ns),
 		      HRTIMER_MODE_REL);
-		if (++fiq_enable == 1)
-			enable_fiq(imx_pcm_fiq);
-
+		enable_fiq(imx_pcm_fiq);
 		break;

 	case SNDRV_PCM_TRIGGER_STOP:
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
-		atomic_set(&iprtd->running, 0);
-
-		if (--fiq_enable == 0)
+		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+			atomic_set(&iprtd->playing, 0);
+		else
+			atomic_set(&iprtd->capturing, 0);
+		if (!atomic_read(&iprtd->playing) &&
+				!atomic_read(&iprtd->capturing))
 			disable_fiq(imx_pcm_fiq);
-
 		break;
+
 	default:
 		return -EINVAL;
 	}
@@ -198,7 +202,8 @@ static int snd_imx_open(struct snd_pcm_substream *substream)

 	iprtd->substream = substream;

-	atomic_set(&iprtd->running, 0);
+	atomic_set(&iprtd->playing, 0);
+	atomic_set(&iprtd->capturing, 0);
 	hrtimer_init(&iprtd->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	iprtd->hrt.function = snd_hrtimer_callback;

--
1.8.3.2