ASoC: SOF: ipc4-pcm: do not report invalid delay values

Add a sanity check for the calculated delay value before reporting it to
the application. If the value is clearly invalid, emit a rate limited
warning to kernel log and return a zero delay. This can occur e.g if the
host or link DMA hits a buffer over/underrun condition.

Signed-off-by: Kai Vehmanen <[email protected]>
Reviewed-by: Péter Ujfalusi <[email protected]>
Reviewed-by: Bard Liao <[email protected]>
Signed-off-by: Peter Ujfalusi <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Mark Brown <[email protected]>

Author: kv2019i

sound/soc/sof/ipc4-pcm.c

@@ -59,6 +59,8 @@ struct sof_ipc4_pcm_stream_priv {
  */
 #define DELAY_BOUNDARY		U32_MAX
 
+#define DELAY_MAX		(DELAY_BOUNDARY >> 1)
+
 static inline struct sof_ipc4_timestamp_info *
 sof_ipc4_sps_to_time_info(struct snd_sof_pcm_stream *sps)
 {
@@ -1266,6 +1268,13 @@ static int sof_ipc4_pcm_pointer(struct snd_soc_component *component,
 	else
 		time_info->delay = head_cnt - tail_cnt;
 
+	if (time_info->delay > DELAY_MAX) {
+		spcm_dbg_ratelimited(spcm, substream->stream,
+				     "inaccurate delay, host %llu dai_cnt %llu",
+				     host_cnt, dai_cnt);
+		time_info->delay = 0;
+	}
+
 	/*
 	 * Convert the host byte counter to PCM pointer which wraps in buffer
 	 * and it is in frames