Re: [PATCH] ASoC: rockchip: rockchip_sai: Set slot width for non-TDM mode

[Nicolas Frattaroli <nicolas.frattaroli@collabora.com>]

On Wednesday, 18 March 2026 15:50:25 Central European Standard Time Alexey Charkov wrote:
> Currently the slot width in non-TDM mode is always kept at the POR value
> of 32 bits, regardless of the sample width, which doesn't work well for
> some codecs such as NAU8822.
> 
> Set the slot width according to the sample width in non-TDM mode, which
> is what other CPU DAI drivers do.
> 
> Tested on the following RK3576 configurations:
> - SAI2 + NAU8822 (codec as the clock master), custom board
> - SAI1 + ES8388 (codec as the clock master), RK3576 EVB1
> - SAI2 + RT5616 (SAI as the clock master), FriendlyElec NanoPi M5
> 
> NAU8822 didn't work prior to this patch but works after the patch. Other
> two configurations work both before and after the patch.
> 
> Fixes: cc78d1eaabad ("ASoC: rockchip: add Serial Audio Interface (SAI) driver")
> Signed-off-by: Alexey Charkov <alchark@flipper.net>
> ---
>  sound/soc/rockchip/rockchip_sai.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/sound/soc/rockchip/rockchip_sai.c b/sound/soc/rockchip/rockchip_sai.c
> index 1bf614dbdf4d..ed393e5034a4 100644
> --- a/sound/soc/rockchip/rockchip_sai.c
> +++ b/sound/soc/rockchip/rockchip_sai.c
> @@ -628,6 +628,10 @@ static int rockchip_sai_hw_params(struct snd_pcm_substream *substream,
>  
>  	regmap_update_bits(sai->regmap, reg, SAI_XCR_VDW_MASK | SAI_XCR_CSR_MASK, val);
>  
> +	if (!sai->is_tdm)
> +		regmap_update_bits(sai->regmap, reg, SAI_XCR_SBW_MASK,
> +				   SAI_XCR_SBW(params_physical_width(params)));
> +
>  	regmap_read(sai->regmap, reg, &val);
>  
>  	slot_width = SAI_XCR_SBW_V(val);
> 
> ---
> base-commit: 8e5a478b6d6a5bb0a3d52147862b15e4d826af19
> change-id: 20260318-sai-slot-width-378eed5c22cd
> 
> Best regards,
> 

Thanks for the patch! Looking at where else this reg mask is used, I
got curious about `rockchip_sai_set_tdm_slot`. It seems to reset
SAI_XCR_SBW back to 32 when something calls it with 0 slots. Do we
have to adjust this as well there?

I think what we're running into here is the difference between I2S
normal mode, and I2S justified mode. In justified modes, it'd be
normal to have a slot bit width of 32 but a valid data width of, say,
16. In that case, VDJ would specify whether something is left or right
justified as far as I can tell.

So basically I'm wondering if we've accidentally been sending
I2S left-justified data all along when using SND_SOC_DAIFMT_I2S,
and whether we should only be setting this in SND_SOC_DAIFMT_I2S.

Either way, I can give this a

Tested-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>

for ES8388 on my ROCK 4D (with my enablement patches for it there
on top that I need to get back around to).

Kind regards,
Nicolas Frattaroli