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

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Date:   Tue, 4 Aug 2020 01:13:34 -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 03:53:51PM +0800, Shengjiu Wang wrote:

> > >                 /* 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.

Ahh..probably should be
if (!(sync[dir] && !sync[adir]) || !frde)

I have a (seemingly) correct version in my sample code.

And...please untangle the logic using the given example -- adding
helper function(s) and comments. And, though the driver does have
places using array[tx] and array[!tx], better not to use any more
boolean type variable as an array index, as it's hard to read.