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

[Shengjiu Wang]

On Wed, Nov 9, 2022 at 8:55 PM Marek Vasut <marex at denx.de> wrote:

> 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.
>

TCSR.TERE and RCSR.TERE all can enable the MCLK.
if use the FSL_SAI_xCSR(tx, ofs), both cases can be covered.
if the bclk is generated by TX, then enable the TE(transmitter) to
generate MCLK.  or if the bclk is generated by RX, then enable
the RE(receiver) 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.
>

May you can try to enhance the drivers/clk/clk-fsl-sai.c

best regards
wang shengjiu