ASoC: qcom: q6apm-dai: fix race condition while updating the position pointer

It is noticed that the position pointer value seems to get a get corrupted
due to missing locking between updating and reading.

Fix this by adding a spinlock around the position pointer.

Fixes: 9b4fe0f1 ("ASoC: qdsp6: audioreach: add q6apm-dai support")
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20230209122806.18923-3-srinivas.kandagatla@linaro.orgSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/qcom/qdsp6/q6apm-dai.c

@@ -8,6 +8,7 @@
 #include <linux/slab.h>
 #include <sound/soc.h>
 #include <sound/soc-dapm.h>
+#include <linux/spinlock.h>
 #include <sound/pcm.h>
 #include <asm/dma.h>
 #include <linux/dma-mapping.h>
@@ -53,6 +54,7 @@ struct q6apm_dai_rtd {
 	uint16_t session_id;
 	enum stream_state state;
 	struct q6apm_graph *graph;
+	spinlock_t lock;
 };
 
 struct q6apm_dai_data {
@@ -99,20 +101,25 @@ static void event_handler(uint32_t opcode, uint32_t token, uint32_t *payload, vo
 {
 	struct q6apm_dai_rtd *prtd = priv;
 	struct snd_pcm_substream *substream = prtd->substream;
+	unsigned long flags;
 
 	switch (opcode) {
 	case APM_CLIENT_EVENT_CMD_EOS_DONE:
 		prtd->state = Q6APM_STREAM_STOPPED;
 		break;
 	case APM_CLIENT_EVENT_DATA_WRITE_DONE:
+	        spin_lock_irqsave(&prtd->lock, flags);
 		prtd->pos += prtd->pcm_count;
+		spin_unlock_irqrestore(&prtd->lock, flags);
 		snd_pcm_period_elapsed(substream);
 		if (prtd->state == Q6APM_STREAM_RUNNING)
 			q6apm_write_async(prtd->graph, prtd->pcm_count, 0, 0, 0);
 
 		break;
 	case APM_CLIENT_EVENT_DATA_READ_DONE:
+	        spin_lock_irqsave(&prtd->lock, flags);
 		prtd->pos += prtd->pcm_count;
+		spin_unlock_irqrestore(&prtd->lock, flags);
 		snd_pcm_period_elapsed(substream);
 		if (prtd->state == Q6APM_STREAM_RUNNING)
 			q6apm_read(prtd->graph);
@@ -253,6 +260,7 @@ static int q6apm_dai_open(struct snd_soc_component *component,
 	if (prtd == NULL)
 		return -ENOMEM;
 
+	spin_lock_init(&prtd->lock);
 	prtd->substream = substream;
 	prtd->graph = q6apm_graph_open(dev, (q6apm_cb)event_handler, prtd, graph_id);
 	if (IS_ERR(prtd->graph)) {
@@ -332,11 +340,17 @@ static snd_pcm_uframes_t q6apm_dai_pointer(struct snd_soc_component *component,
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct q6apm_dai_rtd *prtd = runtime->private_data;
+	snd_pcm_uframes_t ptr;
+	unsigned long flags;
 
+	spin_lock_irqsave(&prtd->lock, flags);
 	if (prtd->pos == prtd->pcm_size)
 		prtd->pos = 0;
 
-	return bytes_to_frames(runtime, prtd->pos);
+	ptr =  bytes_to_frames(runtime, prtd->pos);
+	spin_unlock_irqrestore(&prtd->lock, flags);
+
+	return ptr;
 }
 
 static int q6apm_dai_hw_params(struct snd_soc_component *component,