2 files changed, 25 insertions, 1 deletions

diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index bf8f412988b8..fbbbcd20c4cc 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -629,6 +629,9 @@ int snd_pcm_new_stream(struct snd_pcm *pcm, int stream, int substream_count)
                 substream->number = idx;
                 substream->stream = stream;
                 sprintf(substream->name, "subdevice #%i", idx);
+                snprintf(substream->latency_id, sizeof(substream->latency_id),
+                         "ALSA-PCM%d-%d%c%d", pcm->card->number, pcm->device,
+                         (stream ? 'c' : 'p'), idx);
                 substream->buffer_bytes_max = UINT_MAX;
                 if (prev == NULL)
                         pstr->substream = substream;
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 0224c70414f5..891d7140553c 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -25,6 +25,7 @@
 #include <linux/file.h>
 #include <linux/slab.h>
 #include <linux/time.h>
+#include <linux/latency.h>
 #include <linux/uio.h>
 #include <sound/core.h>
 #include <sound/control.h>
@@ -347,11 +348,26 @@ out:
         return err;
 }
 
+static int period_to_usecs(struct snd_pcm_runtime *runtime)
+{
+        int usecs;
+
+        if (! runtime->rate)
+                return -1; /* invalid */
+
+        /* take 75% of period time as the deadline */
+        usecs = (750000 / runtime->rate) * runtime->period_size;
+        usecs += ((750000 % runtime->rate) * runtime->period_size) /
+                runtime->rate;
+
+        return usecs;
+}
+
 static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
                              struct snd_pcm_hw_params *params)
 {
         struct snd_pcm_runtime *runtime;
-        int err;
+        int err, usecs;
         unsigned int bits;
         snd_pcm_uframes_t frames;
 
@@ -431,6 +447,10 @@ static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
 
         snd_pcm_timer_resolution_change(substream);
         runtime->status->state = SNDRV_PCM_STATE_SETUP;
+
+        remove_acceptable_latency(substream->latency_id);
+        if ((usecs = period_to_usecs(runtime)) >= 0)
+                set_acceptable_latency(substream->latency_id, usecs);
         return 0;
  _error:
         /* hardware might be unuseable from this time,
@@ -490,6 +510,7 @@ static int snd_pcm_hw_free(struct snd_pcm_substream *substream)
         if (substream->ops->hw_free)
                 result = substream->ops->hw_free(substream);
         runtime->status->state = SNDRV_PCM_STATE_OPEN;
+        remove_acceptable_latency(substream->latency_id);
         return result;
 }