[alsa-devel] [PATCH RFC (do not merge)] ASoC: davinci-mcasp: Set rule constraint if implicit bclk divider is used

[Jyri Sarha]

On 03/13/15 13:56, Lars-Peter Clausen wrote:
> On 03/13/2015 12:36 PM, Jyri Sarha wrote:
> [...]
>> In theory this patch does exactly what it is supposed to. It only
>> allows a sample-rate and sample-format combination if the rate can be
>> produced with reasonable accuracy. Unfortunately the alsa-lib and
>> alsa-tools are not able use this information too well. If the requested
>> sample-rate and sample-format is not available the aplay/arecord
>> fails, even if plughw is selected, with:
>>
>> pcm_params.c:170: snd1_pcm_hw_param_get_min: Assertion
>> `!snd_interval_empty(i)' failed.
> [...]
>> +
>> +    /*
>> +     * If we rely on implicit BCLK divider setting we should
>> +     * set constraints based on what we can provide.
>> +     */
>> +    if (mcasp->bclk_master && mcasp->bclk_div == 0 &&
>> mcasp->sysclk_freq)
>> +        return snd_pcm_hw_rule_add(substream->runtime, 0,
>> +                       SNDRV_PCM_HW_PARAM_RATE,
>> +                       davinci_mcasp_hw_rule_rate,
>> +                       mcasp,
>> +                       SNDRV_PCM_HW_PARAM_FRAME_BITS,
>> +                       SNDRV_PCM_HW_PARAM_CHANNELS, -1);
>> +
>
> For things to work correctly you also need reverse rules restricting
> CHANNELS and FRAME_BITS based on the RATE. This might fix the issue you
> are seeing with the ALSA tools.
>

Thanks, that was indeed the case. I mail a new patch once I get my patch 
in order.

Best regards,
Jyri