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

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@scara.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Cc: stable@vger.kernel.org

1 files changed, 17 insertions, 12 deletions

diff --git a/sound/soc/fsl/imx-pcm-fiq.c b/sound/soc/fsl/imx-pcm-fiq.c
index 34043c55f2a6..2fc872b2deff 100644
--- a/sound/soc/fsl/imx-pcm-fiq.c
+++ b/sound/soc/fsl/imx-pcm-fiq.c
@@ -44,7 +44,8 @@ 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)
@@ -56,7 +57,7 @@ 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);
@@ -124,7 +125,6 @@ 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)
@@ -136,23 +136,27 @@ 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;
         }
@@ -200,7 +204,8 @@ 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;