While HDAudio controller supports buffer packets up to 128 bytes low, audio format shall be taken into consideration when calculating buffer and period sizes to avoid undesired xruns.
As *_size in ALSA terms means frames (channels times bit-depth-bytes), hw_rules can calculate minimal buffer and period sizes solely from sample rate and the number of milliseconds commonly used on the AudioDSP firmware side.
Signed-off-by: Cezary Rojewski cezary.rojewski@intel.com --- sound/soc/intel/avs/pcm.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+)
diff --git a/sound/soc/intel/avs/pcm.c b/sound/soc/intel/avs/pcm.c index 405de1d58178..77a7e8f93951 100644 --- a/sound/soc/intel/avs/pcm.c +++ b/sound/soc/intel/avs/pcm.c @@ -457,6 +457,26 @@ static const struct snd_pcm_hw_constraint_list hw_rates = {
const struct snd_soc_dai_ops avs_dai_fe_ops;
+static int hw_rule_param_size(struct snd_pcm_hw_params *params, struct snd_pcm_hw_rule *rule) +{ + struct snd_interval *interval = hw_param_interval(params, rule->var); + struct snd_interval to; + + snd_interval_any(&to); + to.integer = interval->integer; + to.max = interval->max; + /* + * Commonly 2ms buffer size is used in HDA scenarios whereas 4ms is used + * when streaming through GPDMA. Align to the latter to account for both. + */ + to.min = params_rate(params) / 1000 * 4; + + if (rule->var == SNDRV_PCM_HW_PARAM_PERIOD_SIZE) + to.min /= params_periods(params); + + return snd_interval_refine(interval, &to); +} + static int avs_dai_fe_startup(struct snd_pcm_substream *substream, struct snd_soc_dai *dai) { struct snd_pcm_runtime *runtime = substream->runtime; @@ -492,6 +512,14 @@ static int avs_dai_fe_startup(struct snd_pcm_substream *substream, struct snd_so if (ret < 0) goto err;
+ /* Adjust buffer and period size based on the audio format. */ + snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_BUFFER_SIZE, hw_rule_param_size, NULL, + SNDRV_PCM_HW_PARAM_FORMAT, SNDRV_PCM_HW_PARAM_CHANNELS, + SNDRV_PCM_HW_PARAM_RATE, -1); + snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, hw_rule_param_size, NULL, + SNDRV_PCM_HW_PARAM_FORMAT, SNDRV_PCM_HW_PARAM_CHANNELS, + SNDRV_PCM_HW_PARAM_RATE, -1); + snd_pcm_set_sync(substream);
dev_dbg(dai->dev, "%s fe STARTUP tag %d str %p",