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

[Alexey Charkov]

On Wed, Mar 18, 2026 at 11:56 PM Nicolas Frattaroli
<nicolas.frattaroli at collabora.com> wrote:
>
> 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 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,
> >
>
> 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?

Hmm, from what I'm understanding set_tdm_slot is called before
hw_params - e.g. the Freescale SAI driver doesn't even program the
slot width to the hardware from set_tdm_slot and only updates the
requested value in its internal data structure - to be then written
out when hw_params runs. So I believe it should work as-is, although I
haven't seen any TDM users of the Rockchip SAI in the wild to verify
:)

> 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.

Isn't the difference between SND_SOC_DAIFMT_I2S vs.
SND_SOC_DAIFMT_LEFT_J just about clock timings / edges? I thought both
can have slot width >= sample width, but I could be wrong (not an
audio guru here).

> Either way, I can give this a
>
> Tested-by: Nicolas Frattaroli <nicolas.frattaroli at 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).

Thanks a lot!

Best regards,
Alexey