3 files changed, 45 insertions, 0 deletions

diff --git a/include/sound/soc-dai.h b/include/sound/soc-dai.h
index 13676472ddfc..22b729fbbf84 100644
--- a/include/sound/soc-dai.h
+++ b/include/sound/soc-dai.h
@@ -208,6 +208,7 @@ struct snd_soc_dai {
         /* DAI capabilities */
         struct snd_soc_pcm_stream capture;
         struct snd_soc_pcm_stream playback;
+        unsigned int symmetric_rates:1;
 
         /* DAI runtime info */
         struct snd_pcm_runtime *runtime;
diff --git a/include/sound/soc.h b/include/sound/soc.h
index a40bc6f316fc..b1f2f8819fea 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -417,6 +417,12 @@ struct snd_soc_dai_link  {
         /* codec/machine specific init - e.g. add machine controls */
         int (*init)(struct snd_soc_codec *codec);
 
+        /* Symmetry requirements */
+        unsigned int symmetric_rates:1;
+
+        /* Symmetry data - only valid if symmetry is being enforced */
+        unsigned int rate;
+
         /* DAI pcm */
         struct snd_pcm *pcm;
 };
diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index 99712f652d0d..dd28009f8969 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -113,6 +113,35 @@ static int soc_ac97_dev_register(struct snd_soc_codec *codec)
 }
 #endif
 
+static int soc_pcm_apply_symmetry(struct snd_pcm_substream *substream)
+{
+        struct snd_soc_pcm_runtime *rtd = substream->private_data;
+        struct snd_soc_device *socdev = rtd->socdev;
+        struct snd_soc_card *card = socdev->card;
+        struct snd_soc_dai_link *machine = rtd->dai;
+        struct snd_soc_dai *cpu_dai = machine->cpu_dai;
+        struct snd_soc_dai *codec_dai = machine->codec_dai;
+        int ret;
+
+        if (codec_dai->symmetric_rates || cpu_dai->symmetric_rates ||
+            machine->symmetric_rates) {
+                dev_dbg(card->dev, "Symmetry forces %dHz rate\n", 
+                        machine->rate);
+
+                ret = snd_pcm_hw_constraint_minmax(substream->runtime,
+                                                   SNDRV_PCM_HW_PARAM_RATE,
+                                                   machine->rate,
+                                                   machine->rate);
+                if (ret < 0) {
+                        dev_err(card->dev,
+                                "Unable to apply rate symmetry constraint: %d\n", ret);
+                        return ret;
+                }
+        }
+
+        return 0;
+}
+
 /*
  * Called by ALSA when a PCM substream is opened, the runtime->hw record is
  * then initialized and any private data can be allocated. This also calls
@@ -221,6 +250,13 @@ static int soc_pcm_open(struct snd_pcm_substream *substream)
                 goto machine_err;
         }
 
+        /* Symmetry only applies if we've already got an active stream. */
+        if (cpu_dai->active || codec_dai->active) {
+                ret = soc_pcm_apply_symmetry(substream);
+                if (ret != 0)
+                        goto machine_err;
+        }
+
         pr_debug("asoc: %s <-> %s info:\n", codec_dai->name, cpu_dai->name);
         pr_debug("asoc: rate mask 0x%x\n", runtime->hw.rates);
         pr_debug("asoc: min ch %d max ch %d\n", runtime->hw.channels_min,
@@ -521,6 +557,8 @@ static int soc_pcm_hw_params(struct snd_pcm_substream *substream,
                 }
         }
 
+        machine->rate = params_rate(params);
+
 out:
         mutex_unlock(&pcm_mutex);
         return ret;