From: Chancel Liu <chancel.liu@nxp.com>

When configuring 32 slots TDM (channels == slots == 32), the xMR
(Mask Register) write used:
~0UL - ((1 << min(channels, slots)) - 1)

The literal "1" is a signed 32-bit int. Shifting it by 32 positions is
undefined behaviour which may set this register to 0xFFFFFFFF, masking
all 32 slots.

Use GENMASK_U32() macro instead. For 32 slots this produces a zero mask:
~GENMASK_U32(31, 0) = ~0xFFFFFFFF = 0x00000000
Behaviour for fewer than 32 slots is unchanged.

Fixes: 770f58d7d2c5 ("ASoC: fsl_sai: Support multiple data channel enable bits")
Cc: stable@vger.kernel.org
Signed-off-by: Chancel Liu <chancel.liu@nxp.com>
---
Changes in v3
- Fix patch can't be applied

Changes in v2
- Use GENMASK_U32() macro instead to make it clearer and safer

 sound/soc/fsl/fsl_sai.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
index d6dd95680892..9661602b53c5 100644
--- a/sound/soc/fsl/fsl_sai.c
+++ b/sound/soc/fsl/fsl_sai.c
@@ -797,7 +797,7 @@ static int fsl_sai_hw_params(struct snd_pcm_substream *substream,
 				   FSL_SAI_CR4_FSD_MSTR, FSL_SAI_CR4_FSD_MSTR);

 	regmap_write(sai->regmap, FSL_SAI_xMR(tx),
-		     ~0UL - ((1 << min(channels, slots)) - 1));
+		     ~GENMASK_U32(min(channels, slots) - 1, 0));

 	return 0;
 }
--
2.50.1

On Mon, 01 Jun 2026 17:33:27 +0900, chancel.liu@oss.nxp.com wrote:
> ASoC: fsl_sai: Fix 32 slots TDM broken by integer shift UB in xMR write

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-7.1

Thanks!

[1/1] ASoC: fsl_sai: Fix 32 slots TDM broken by integer shift UB in xMR write
      https://git.kernel.org/broonie/sound/c/4790af1cc2e8

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

On Mon, Jun 1, 2026 at 4:33 PM <chancel.liu@oss.nxp.com> wrote:
>
> From: Chancel Liu <chancel.liu@nxp.com>
>
> When configuring 32 slots TDM (channels == slots == 32), the xMR
> (Mask Register) write used:
> ~0UL - ((1 << min(channels, slots)) - 1)
>
> The literal "1" is a signed 32-bit int. Shifting it by 32 positions is
> undefined behaviour which may set this register to 0xFFFFFFFF, masking
> all 32 slots.
>
> Use GENMASK_U32() macro instead. For 32 slots this produces a zero mask:
> ~GENMASK_U32(31, 0) = ~0xFFFFFFFF = 0x00000000
> Behaviour for fewer than 32 slots is unchanged.
>
> Fixes: 770f58d7d2c5 ("ASoC: fsl_sai: Support multiple data channel enable bits")
> Cc: stable@vger.kernel.org
> Signed-off-by: Chancel Liu <chancel.liu@nxp.com>

Reviewed-by: Shengjiu Wang <shengjiu.wang@gmail.com>

Best regards
Shengjiu Wang
> ---
> Changes in v3
> - Fix patch can't be applied
>
> Changes in v2
> - Use GENMASK_U32() macro instead to make it clearer and safer
>
>  sound/soc/fsl/fsl_sai.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
> index d6dd95680892..9661602b53c5 100644
> --- a/sound/soc/fsl/fsl_sai.c
> +++ b/sound/soc/fsl/fsl_sai.c
> @@ -797,7 +797,7 @@ static int fsl_sai_hw_params(struct snd_pcm_substream *substream,
>                                    FSL_SAI_CR4_FSD_MSTR, FSL_SAI_CR4_FSD_MSTR);
>
>         regmap_write(sai->regmap, FSL_SAI_xMR(tx),
> -                    ~0UL - ((1 << min(channels, slots)) - 1));
> +                    ~GENMASK_U32(min(channels, slots) - 1, 0));
>
>         return 0;
>  }
> --
> 2.50.1
>