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

[Nicolas Frattaroli]

On Wednesday, 18 March 2026 15:50:25 Central European Summer 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 at 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,
> 

Okay, so I took a logic analyzer to the SAI today and found the following:

It seems we've always been sending 16-bit samples in 32-bit width slots per
channel before. With this change, we're now correctly sending 16-bit samples
in 16-bit slots.

In a follow-up patch (doesn't have to be in this one, this is fine to merge
as-is) we could also refactor the switch statement just above to no longer
exist but set val = SAI_XCR_VDW(params_width(params)).

So:

Acked-by: Nicolas Frattaroli <nicolas.frattaroli at collabora.com>

Kind regards,
Nicolas Frattaroli