[PATCH 3.10 018/173] ASoC: fsl: imx-pcm-fiq: omit fiq counter to avoid harm in unbalanced situations

Greg Kroah-Hartman
2013-12-02T19:12:55Z

From: Oskar Schirmer <oskar@scara.com>

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@scara.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
sound/soc/fsl/imx-pcm-fiq.c | 29 +++++++++++++++++------------
1 file changed, 17 insertions(+), 12 deletions(-)

--- 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_
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 sn
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 sn
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_s

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;