ASoC: SOF: PCM: add period_elapsed work to fix race condition in interrupt context

The IPC implementation in SOF requires sending IPCs serially: we should
not send a new IPC command to the firmware before we get an ACK (or time
out) from firmware, and the IRQ processing is complete.

snd_pcm_period_elapsed() can be called in interrupt context before
IRQ_HANDLED is returned. When the PCM is done draining, a STOP
IPC will then be sent, which breaks the expectation that IPCs are
handled serially and leads to IPC timeouts.

This patch adds a workqueue to defer the call to snd_pcm_elapsed() after
the IRQ is handled.

Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/sound/soc/sof/pcm.c b/sound/soc/sof/pcm.c
index be4984c..6499688 100644 (file)
--- a/sound/soc/sof/pcm.c
+++ b/sound/soc/sof/pcm.c
@@ -52,6 +52,48 @@ static int sof_pcm_dsp_params(struct snd_sof_pcm *spcm, struct snd_pcm_substream
        return ret;
 }
 
+/*
+ * sof pcm period elapse work
+ */
+static void sof_pcm_period_elapsed_work(struct work_struct *work)
+{
+       struct snd_sof_pcm_stream *sps =
+               container_of(work, struct snd_sof_pcm_stream,
+                            period_elapsed_work);
+
+       snd_pcm_period_elapsed(sps->substream);
+}
+
+/*
+ * sof pcm period elapse, this could be called at irq thread context.
+ */
+void snd_sof_pcm_period_elapsed(struct snd_pcm_substream *substream)
+{
+       struct snd_soc_pcm_runtime *rtd = substream->private_data;
+       struct snd_soc_component *component =
+               snd_soc_rtdcom_lookup(rtd, DRV_NAME);
+       struct snd_sof_dev *sdev = snd_soc_component_get_drvdata(component);
+       struct snd_sof_pcm *spcm;
+
+       spcm = snd_sof_find_spcm_dai(sdev, rtd);
+       if (!spcm) {
+               dev_err(sdev->dev,
+                       "error: period elapsed for unknown stream!\n");
+               return;
+       }
+
+       /*
+        * snd_pcm_period_elapsed() can be called in interrupt context
+        * before IRQ_HANDLED is returned. Inside snd_pcm_period_elapsed(),
+        * when the PCM is done draining or xrun happened, a STOP IPC will
+        * then be sent and this IPC will hit IPC timeout.
+        * To avoid sending IPC before the previous IPC is handled, we
+        * schedule delayed work here to call the snd_pcm_period_elapsed().
+        */
+       schedule_work(&spcm->stream[substream->stream].period_elapsed_work);
+}
+EXPORT_SYMBOL(snd_sof_pcm_period_elapsed);
+
 /* this may get called several times by oss emulation */
 static int sof_pcm_hw_params(struct snd_pcm_substream *substream,
                             struct snd_pcm_hw_params *params)
@@ -169,6 +211,9 @@ static int sof_pcm_hw_params(struct snd_pcm_substream *substream,
        /* save pcm hw_params */
        memcpy(&spcm->params[substream->stream], params, sizeof(*params));
 
+       INIT_WORK(&spcm->stream[substream->stream].period_elapsed_work,
+                 sof_pcm_period_elapsed_work);
+
        return ret;
 }
 
@@ -203,6 +248,9 @@ static int sof_pcm_hw_free(struct snd_pcm_substream *substream)
                                 sizeof(stream), &reply, sizeof(reply));
 
        snd_pcm_lib_free_pages(substream);
+
+       cancel_work_sync(&spcm->stream[substream->stream].period_elapsed_work);
+
        return ret;
 }
 

diff --git a/sound/soc/sof/sof-priv.h b/sound/soc/sof/sof-priv.h
index 35e78ff..675bb10 100644 (file)
--- a/sound/soc/sof/sof-priv.h
+++ b/sound/soc/sof/sof-priv.h
@@ -274,6 +274,7 @@ struct snd_sof_pcm_stream {
        struct snd_dma_buffer page_table;
        struct sof_ipc_stream_posn posn;
        struct snd_pcm_substream *substream;
+       struct work_struct period_elapsed_work;
 };
 
 /* ALSA SOF PCM device */
@@ -495,6 +496,7 @@ struct snd_sof_pcm *snd_sof_find_spcm_comp(struct snd_sof_dev *sdev,
                                           int *direction);
 struct snd_sof_pcm *snd_sof_find_spcm_pcm_id(struct snd_sof_dev *sdev,
                                             unsigned int pcm_id);
+void snd_sof_pcm_period_elapsed(struct snd_pcm_substream *substream);
 
 /*
  * Stream IPC