linux-kernel - Re: [PATCH] ASoC: fsl_sai: Remove unnecessary FIFO reset in ISR

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Message-ID: <CAGoOwPT1tP-HP+0J1ddZ0Ea+67zzLzFFTeptTpNwkzxRK45b5g@mail.gmail.com>
Date:   Tue, 16 Aug 2022 23:20:56 -0700
From:   Nicolin Chen <nicoleotsuka@...il.com>
To:     Shengjiu Wang <shengjiu.wang@....com>
Cc:     Xiubo.Lee@...il.com, festevam@...il.com, shengjiu.wang@...il.com,
        lgirdwood@...il.com, broonie@...nel.org, perex@...ex.cz,
        tiwai@...e.com, alsa-devel@...a-project.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC: fsl_sai: Remove unnecessary FIFO reset in ISR

On Tue, Aug 16, 2022 at 10:41 PM Shengjiu Wang <shengjiu.wang@....com> wrote:
>
> The FIFO reset drops the words in the FIFO, which may cause
> channel swap when SAI module is running, especially when the
> DMA speed is low. So it is not good to do FIFO reset in ISR,
> then remove the operation.

I don't recall the details of adding this many years ago, but
leaving underrun/overrun errors unhandled does not sound right
to me either. Would it result in a channel swap also? Perhaps
there needs to be a reset routine that stops and restarts the
DMA as well?