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From:   Nicolin Chen <nicoleotsuka@gmail.com>
Date:   Tue, 16 Aug 2022 23:35:22 -0700
Message-ID: <CAGoOwPSgPSV2HOqC=t_NVor8YqxaLxmeDvMf8_j25phsPpcd4g@mail.gmail.com>
Subject: Re: [PATCH] ASoC: fsl_sai: Remove unnecessary FIFO reset in ISR
To:     Shengjiu Wang <shengjiu.wang@gmail.com>
Cc:     Shengjiu Wang <shengjiu.wang@nxp.com>,
        Xiubo Li <Xiubo.Lee@gmail.com>,
        Fabio Estevam <festevam@gmail.com>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>, alsa-devel@alsa-project.org,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
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On Tue, Aug 16, 2022 at 11:29 PM Shengjiu Wang <shengjiu.wang@gmail.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?
>
>
> Remove the reset, the channel swap is gone.

I have no doubt about that :)

> IMO, no need to handle the underrun/overrun in driver, the SAI
> hardware can handle the read/write pointer itself when xrun happen,
> and we don't need reset routine.

That'd be okay then.