[PATCH] ASoC: pcm512x: Mend accesses to the I2S_1 and I2S_2 registers

[Péter Ujfalusi]

Hi Peter,

On 9/20/21 17:49, Peter Rosin wrote:
> From 625f858894af2b7e547cc723b97361081438b123 Mon Sep 17 00:00:00 2001
> From: Peter Rosin <peda at axentia.se>
> 
> Commit 25d27c4f68d2 ("ASoC: pcm512x: Add support for more data formats")
> breaks the TSE-850 device, which is using a pcm5142 in I2S and
> CBM_CFS mode (maybe not relevant). Without this fix, the result
> is:
> 
> pcm512x 0-004c: Failed to set data format: -16
> 
> And after that, no sound.

Is it possible that on the board the pcm5142 is in hardwired mode (MODE1
and MODE2 pin is pulled low)? If it is and FMT pin is also low then the
codec is in i2s mode.

I can imagine that the codec would ignore a write to AFMT part of I2S_1
register - it is wired for 00b.

> This fix is not 100% correct. The datasheet of at least the pcm5142
> states that four bits (0xcc) in the I2S_1 register are "RSV"
> ("Reserved. Do not access.") and no hint is given as to what the
> initial values are supposed to be. So, specifying defaults for
> these bits is wrong. But perhaps better than a broken driver?

The default of 0x02 (AFMT = 00b - I2S, ALEN = 10b - 24bits) is correct
for I2S_1 and the 0 is the default of I2S_2.

The failure happens when updating the AFMT (bit4-5) and when regmap is
doing a i2c read since the default is not specified.

It would be interesting to see what it is reading... Out of interest:
can you mar the I2S_1 and I2S_2 as volatile and read / print the value
just before the afmt and alen update?

> Fixes: 25d27c4f68d2 ("ASoC: pcm512x: Add support for more data formats")
> Cc: Liam Girdwood <lgirdwood at gmail.com>
> Cc: Mark Brown <broonie at kernel.org>
> Cc: Jaroslav Kysela <perex at perex.cz>
> Cc: Takashi Iwai <tiwai at suse.com>
> Cc: Kirill Marinushkin <kmarinushkin at birdec.com>
> Cc: Peter Ujfalusi <peter.ujfalusi at ti.com>
> Cc: alsa-devel at alsa-project.org
> Cc: linux-kernel at vger.kernel.org
> Signed-off-by: Peter Rosin <peda at axentia.se>

The defaults for the two registers are OK, should be safe ;)

Reviewed-by: Peter Ujfalusi <peter.ujfalusi at gmail.com>

> ---
>  sound/soc/codecs/pcm512x.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/sound/soc/codecs/pcm512x.c b/sound/soc/codecs/pcm512x.c
> index 4dc844f3c1fc..60dee41816dc 100644
> --- a/sound/soc/codecs/pcm512x.c
> +++ b/sound/soc/codecs/pcm512x.c
> @@ -116,6 +116,8 @@ static const struct reg_default pcm512x_reg_defaults[] = {
>  	{ PCM512x_FS_SPEED_MODE,     0x00 },
>  	{ PCM512x_IDAC_1,            0x01 },
>  	{ PCM512x_IDAC_2,            0x00 },
> +	{ PCM512x_I2S_1,             0x02 },
> +	{ PCM512x_I2S_2,             0x00 },
>  };
>  
>  static bool pcm512x_readable(struct device *dev, unsigned int reg)
> 

-- 
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