[PATCH] ASoC: fsl_sai: Enable transmitter when generating MCLK

[Marek Vasut]

On 11/9/22 10:30, Shengjiu Wang wrote:

[...]

>> diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
>> index 1c9be8a5dcb13..98c62027e5799 100644
>> --- a/sound/soc/fsl/fsl_sai.c
>> +++ b/sound/soc/fsl/fsl_sai.c
>> @@ -503,6 +503,10 @@ static int fsl_sai_set_bclk(struct snd_soc_dai *dai,
>> bool tx, u32 freq)
>>                  /* SAI is in master mode at this point, so enable MCLK */
>>                  regmap_update_bits(sai->regmap, FSL_SAI_MCTL,
>>                                     FSL_SAI_MCTL_MCLK_EN,
>> FSL_SAI_MCTL_MCLK_EN);
>> +
>> +               /* Transmitter must be enabled to generate MCLK on pad */
>> +               regmap_update_bits(sai->regmap, FSL_SAI_xCSR(1, ofs),
>> +                                  FSL_SAI_CSR_TERE, FSL_SAI_CSR_TERE);
>>
> 
> No need to fix the transmitter,   FSL_SAI_xCSR(tx, ofs) should work also.

That's probably not a good idea, since this could also enable the 
RE(receiver) part . We always need to enable the TE(transmitter) to 
generate MCLK.

>>          }
>>
>>          return 0;
>> @@ -1445,6 +1449,11 @@ static int fsl_sai_probe(struct platform_device
>> *pdev)
>>              sai->soc_data->max_register >= FSL_SAI_MCTL) {
>>                  regmap_update_bits(sai->regmap, FSL_SAI_MCTL,
>>                                     FSL_SAI_MCTL_MCLK_EN,
>> FSL_SAI_MCTL_MCLK_EN);
>> +
>> +               /* Transmitter must be enabled to generate MCLK on pad */
>> +               regmap_update_bits(sai->regmap,
>> +                                  FSL_SAI_xCSR(1,
>> sai->soc_data->reg_offset),
>> +                                  FSL_SAI_CSR_TERE, FSL_SAI_CSR_TERE);
>>
> 
> After one time playback or recording,  the TERE is disabled, so this changes
> in probe() only for the first time.  There is the same issue for the second
> time.

So what would you suggest to keep the MCLK clock generated always ?

I was almost tempted to turn the SAI into a clock provider, so that the 
codec could become its clock consumer and enable the MCLK on demand, but 
that seems to be a rather invasive change.