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

[Kamal Mostafa]

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-3.8.y-queue branch of the 3.8.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-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.14.

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

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 3c6d640180e75f39d18f103cf919fca5bc8c7c99 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: Kamal Mostafa <kamal 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 920f945..6948a6a 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