linux-kernel - Re: [PATCH V2 2/2] ASoC: fsl_esai: recover the channel swap after xrun

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Date:   Tue, 9 Jul 2019 03:38:36 +0000
From:   "S.j. Wang" <shengjiu.wang@....com>
To:     Nicolin Chen <nicoleotsuka@...il.com>
CC:     "timur@...nel.org" <timur@...nel.org>,
        "Xiubo.Lee@...il.com" <Xiubo.Lee@...il.com>,
        "festevam@...il.com" <festevam@...il.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 2/2] ASoC: fsl_esai: recover the channel swap after
 xrun


> > > > +
> > > > +     /* restore registers by regcache_sync */
> > > > +     fsl_esai_register_restore(esai_priv);
> > > > +
> > > > +     regmap_update_bits(esai_priv->regmap, REG_ESAI_TCR,
> > > > +                        ESAI_xCR_xPR_MASK, 0);
> > > > +     regmap_update_bits(esai_priv->regmap, REG_ESAI_RCR,
> > > > +                        ESAI_xCR_xPR_MASK, 0);
> > >
> > > And just for curious, can (or shall) we stuff this personal reset to
> > > the reset() function? I found this one is a part of the reset
> > > routine being mentioned in the RM -- it was done after ESAI reset is
> done via ECR register.
> > >
> >
> > There is a problem to do this, TPR/RPR need to be clear after
> > configure the control register. (TCCR, TCR). So it seems not only one
> > place (reset function) need to be changed.
> 
> Do you know (or remember) why we suddenly involve this TPR/PRP?
> The driver has no problem so far, even if we don't have them.
> 
> The "personal reset" sounds like a feature that we would use to reset TX or
> RX individually, while this hw_reset() does a full reset for both TX and RX.
> So I wonder whether they're necessary.

The hw_reset flow is suggested by design team, so involve TRP/RPP is from
them, I don't know the detail.

Best regards
Wang shengjiu