linux-kernel - Re: [PATCH] ASoC: fsl_sai: Clean code for synchronize mode

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Message-ID: <20200804070825.GB27658@Asurada-Nvidia>
Date:   Tue, 4 Aug 2020 00:08:25 -0700
From:   Nicolin Chen <nicoleotsuka@...il.com>
To:     Shengjiu Wang <shengjiu.wang@...il.com>
Cc:     Shengjiu Wang <shengjiu.wang@....com>,
        Linux-ALSA <alsa-devel@...a-project.org>,
        Timur Tabi <timur@...nel.org>, Xiubo Li <Xiubo.Lee@...il.com>,
        linuxppc-dev@...ts.ozlabs.org, Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Fabio Estevam <festevam@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ASoC: fsl_sai: Clean code for synchronize mode

On Tue, Aug 04, 2020 at 12:03:46AM -0700, Nicolin Chen 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 "&&".
> 
> 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.

Aww..this should be a generic function, so drop "current":

  * or Receiver's for both streams. This function is used to check if clocks of
  * the stream's are synced by the opposite stream.

>  *
>  * @sai: SAI context
>  * @dir: direction of current stream

Ditto:
   * @dir: stream direction

Thanks.
-----
   
>  */
> 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 :)