Re: [PATCH v4] ASoC: fsl_sai: Force a software reset when starting in consumer mode

[Shengjiu Wang]

On Thu, Jun 26, 2025 at 9:09 PM Arun Raghavan <arun@xxxxxxxxxxxxxxxx> wrote:
>
> From: Arun Raghavan <arun@xxxxxxxxxxxxx>
>
> On an imx8mm platform with an external clock provider, when running the
> receiver (arecord) and triggering an xrun with xrun_injection, we see a
> channel swap/offset. This happens sometimes when running only the
> receiver, but occurs reliably if a transmitter (aplay) is also
> concurrently running.
>
> It seems that the SAI loses track of frame sync during the trigger stop
> -> trigger start cycle that occurs during an xrun. Doing just a FIFO
> reset in this case does not suffice, and only a software reset seems to
> get it back on track.
>
> This looks like the same h/w bug that is already handled for the
> producer case, so we now do the reset unconditionally on config disable.
>
> Signed-off-by: Arun Raghavan <arun@xxxxxxxxxxxxx>
> Reported-by: Pieterjan Camerlynck <p.camerlynck@xxxxxxxxxxx>
> Fixes: 3e3f8bd56955 ("ASoC: fsl_sai: fix no frame clk in master mode")
> Cc: stable@xxxxxxxxxxxxxxx

Acked-by: Shengjiu Wang <shengjiu.wang@xxxxxxxxx>

Best regards
Shengjiu Wang
> ---
>
> v4
> - Add Fixes and cc stable
>
> v3
> - Incorporate feedback from Shengjiu Wang to consolidate with the
>   existing handling of this issue in producer mode
>
> v2 (no longer relevant)
> - Address build warning from kernel test robot
>
>  sound/soc/fsl/fsl_sai.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
> index af1a168d35e3..50af6b725670 100644
> --- a/sound/soc/fsl/fsl_sai.c
> +++ b/sound/soc/fsl/fsl_sai.c
> @@ -803,13 +803,15 @@ static void fsl_sai_config_disable(struct fsl_sai *sai, int dir)
>          * anymore. Add software reset to fix this issue.
>          * This is a hardware bug, and will be fix in the
>          * next sai version.
> +        *
> +        * In consumer mode, this can happen even after a
> +        * single open/close, especially if both tx and rx
> +        * are running concurrently.
>          */
> -       if (!sai->is_consumer_mode[tx]) {
> -               /* Software Reset */
> -               regmap_write(sai->regmap, FSL_SAI_xCSR(tx, ofs), FSL_SAI_CSR_SR);
> -               /* Clear SR bit to finish the reset */
> -               regmap_write(sai->regmap, FSL_SAI_xCSR(tx, ofs), 0);
> -       }
> +       /* Software Reset */
> +       regmap_write(sai->regmap, FSL_SAI_xCSR(tx, ofs), FSL_SAI_CSR_SR);
> +       /* Clear SR bit to finish the reset */
> +       regmap_write(sai->regmap, FSL_SAI_xCSR(tx, ofs), 0);
>  }
>
>  static int fsl_sai_trigger(struct snd_pcm_substream *substream, int cmd,
> --
> 2.49.0
>