ALSA: pcm: don't override timestamp unconditionally

timestamp in RUNNING mode is already taken in update_hw_ptr routine,
getting a new timestamp introduces offset between hw_ptr, audio_tstamp
and system time

Add else condition to read timestamp as fallback and only when
enabled
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/pcm_native.c

@@ -720,8 +720,11 @@ int snd_pcm_status(struct snd_pcm_substream *substream,
 				runtime->status->audio_tstamp;
 			goto _tstamp_end;
 		}
+	} else {
+		/* get tstamp only in fallback mode and only if enabled */
+		if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE)
+			snd_pcm_gettime(runtime, &status->tstamp);
 	}
-	snd_pcm_gettime(runtime, &status->tstamp);
  _tstamp_end:
 	status->appl_ptr = runtime->control->appl_ptr;
 	status->hw_ptr = runtime->status->hw_ptr;