[PATCH] ASoC: fsl_sai: Clean code for synchronize mode

[Shengjiu Wang]

On Tue, Aug 4, 2020 at 3:04 PM Nicolin Chen <nicoleotsuka at gmail.com> wrote:
>
> On Tue, Aug 04, 2020 at 12:22:53PM +0800, Shengjiu Wang wrote:
>
> > > > Btw, do we need similar change for TRIGGER_STOP?
> > >
> > > This is a good question. It is better to do change for STOP,
> > > but I am afraid that there is no much test to guarantee the result.
>
> > Maybe we can do this change for STOP.
>
> The idea looks good to me...(check inline comments)
>
> > diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
> > index 1c0e06bb3783..6e4be398eaee 100644
> > --- a/sound/soc/fsl/fsl_sai.c
> > +++ b/sound/soc/fsl/fsl_sai.c
> > @@ -517,6 +517,37 @@ static int fsl_sai_hw_free(struct
> > snd_pcm_substream *substream,
> >         return 0;
> >  }
> >
> > +static void fsl_sai_config_disable(struct fsl_sai *sai, bool tx)
> > +{
> > +       unsigned int ofs = sai->soc_data->reg_offset;
> > +       u32 xcsr, count = 100;
> > +
> > +       regmap_update_bits(sai->regmap, FSL_SAI_xCSR(tx, ofs),
> > +                          FSL_SAI_CSR_TERE, 0);
> > +
> > +       /* TERE will remain set till the end of current frame */
> > +       do {
> > +               udelay(10);
> > +               regmap_read(sai->regmap, FSL_SAI_xCSR(tx, ofs), &xcsr);
> > +       } while (--count && xcsr & FSL_SAI_CSR_TERE);
> > +
> > +       regmap_update_bits(sai->regmap, FSL_SAI_xCSR(tx, ofs),
> > +                          FSL_SAI_CSR_FR, FSL_SAI_CSR_FR);
> > +
> > +       /*
> > +        * For sai master mode, after several open/close sai,
> > +        * there will be no frame clock, and can't recover
> > +        * anymore. Add software reset to fix this issue.
> > +        * This is a hardware bug, and will be fix in the
> > +        * next sai version.
> > +        */
> > +       if (!sai->is_slave_mode) {
> > +               /* Software Reset for both Tx and Rx */
>
> Remove "for both Tx and Rx"
>
> >                 /* Check if the opposite FRDE is also disabled */
> >                 regmap_read(sai->regmap, FSL_SAI_xCSR(!tx, ofs), &xcsr);
> > +               if (sai->synchronous[tx] && !sai->synchronous[!tx] && !(xcsr & FSL_SAI_CSR_FRDE))
> > +                       fsl_sai_config_disable(sai, !tx);
>
> > +               if (sai->synchronous[tx] || !sai->synchronous[!tx] || !(xcsr & FSL_SAI_CSR_FRDE))
> > +                       fsl_sai_config_disable(sai, tx);
>
> The first "||" should probably be "&&".

No. it is !(!sai->synchronous[tx] && sai->synchronous[!tx] && (xcsr &
FSL_SAI_CSR_FRDE))
so then convert to
(sai->synchronous[tx] || !sai->synchronous[!tx] || !(xcsr & FSL_SAI_CSR_FRDE))

if change to &&, then it won't work for:
sai->synchronous[tx] = false, sai->synchronous[!tx]=false.
or
sai->synchronous[tx] = true, sai->synchronous[!tx]=true.
(even we don't have such a case).

>
> The trigger() logic is way more complicated than a simple cleanup
> in my opinion. Would suggest to split RMR part out of this change.
>
> And for conditions like "sync[tx] && !sync[!tx]", it'd be better
> to have a helper function to improve readability:
>
> /**
>  * fsl_sai_dir_is_synced - Check if stream is synced by the opposite stream
>  *
>  * SAI supports synchronous mode using bit/frame clocks of either Transmitter's
>  * or Receiver's for both streams. This function is used to check if clocks of
>  * current stream's are synced by the opposite stream.
>  *
>  * @sai: SAI context
>  * @dir: direction of current stream
>  */
> static inline bool fsl_sai_dir_is_synced(struct fsl_sai *sai, int dir)
> {
>         int adir = (dir == TX) ? RX : TX;
>
>         /* current dir in async mode while opposite dir in sync mode */
>         return !sai->synchronous[dir] && sai->synchronous[adir];
> }
>
> Then add more comments in trigger:
>
> static ...trigger()
> {
>         bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
>         int adir = tx ? RX : TX;
>         int dir = tx ? TX : RX;
>
>         // ....
>         {
>                 // ...
>
>                 /* Check if the opposite FRDE is also disabled */
>                 regmap_read(sai->regmap, FSL_SAI_xCSR(!tx, ofs), &xcsr);
>
>                 /*
>                  * If opposite stream provides clocks for synchronous mode and
>                  * it is inactive, disable it before disabling the current one
>                  */
>                 if (fsl_sai_dir_is_synced(adir) && !(xcsr & FSL_SAI_CSR_FRDE))
>                         fsl_sai_config_disable(sai, adir);
>
>                 /*
>                  * Disable current stream if either of:
>                  * 1. current stream doesn't provide clocks for synchronous mode
>                  * 2. current stream provides clocks for synchronous mode but no
>                  *    more stream is active.
>                  */
>                 if (!fsl_sai_dir_is_synced(dir) || !(xcsr & FSL_SAI_CSR_FRDE))
>                         fsl_sai_config_disable(sai, dir);
>
>                 // ...
>         }
>         // ....
> }
>
> Note, in fsl_sai_config_disable(sai, dir):
>         bool tx = dir == TX;
>
> Above all, I am just drafting, so please test it thoroughly :)