From: Tomasz Merta Date: Wed, 8 Apr 2026 08:40:56 +0000 (+0200) Subject: ASoC: stm32_sai: fix incorrect BCLK polarity for DSP_A/B, LEFT_J X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0669631dbccd41cf3ca7aa70213fcd8bb41c4b38;p=thirdparty%2Flinux.git ASoC: stm32_sai: fix incorrect BCLK polarity for DSP_A/B, LEFT_J The STM32 SAI driver do not set the clock strobing bit (CKSTR) for DSP_A, DSP_B and LEFT_J formats, causing data to be sampled on the wrong BCLK edge when SND_SOC_DAIFMT_NB_NF is used. Per ALSA convention, NB_NF requires sampling on the rising BCLK edge. The STM32MP25 SAI reference manual states that CKSTR=1 is required for signals received by the SAI to be sampled on the SCK rising edge. Without setting CKSTR=1, the SAI samples on the falling edge, violating the NB_NF convention. For comparison, the NXP FSL SAI driver correctly sets FSL_SAI_CR2_BCP for DSP_A, DSP_B and LEFT_J, consistent with its I2S handling. This patch adds SAI_XCR1_CKSTR for DSP_A, DSP_B and LEFT_J in stm32_sai_set_dai_fmt which was verified empirically with a cs47l35 codec. RIGHT_J (LSB) is not investigated and addressed by this patch. Note: the STM32 I2S driver (stm32_i2s_set_dai_fmt) may have the same issue for DSP_A mode, as I2S_CGFR_CKPOL is not set. This has not been verified and is left for a separate investigation. Signed-off-by: Tomasz Merta Link: https://patch.msgid.link/20260408084056.20588-1-tommerta@gmail.com Signed-off-by: Mark Brown --- diff --git a/sound/soc/stm/stm32_sai_sub.c b/sound/soc/stm/stm32_sai_sub.c index 450e1585edee..3e82fa90e719 100644 --- a/sound/soc/stm/stm32_sai_sub.c +++ b/sound/soc/stm/stm32_sai_sub.c @@ -802,6 +802,7 @@ static int stm32_sai_set_dai_fmt(struct snd_soc_dai *cpu_dai, unsigned int fmt) break; /* Left justified */ case SND_SOC_DAIFMT_MSB: + cr1 |= SAI_XCR1_CKSTR; frcr |= SAI_XFRCR_FSPOL | SAI_XFRCR_FSDEF; break; /* Right justified */ @@ -809,9 +810,11 @@ static int stm32_sai_set_dai_fmt(struct snd_soc_dai *cpu_dai, unsigned int fmt) frcr |= SAI_XFRCR_FSPOL | SAI_XFRCR_FSDEF; break; case SND_SOC_DAIFMT_DSP_A: + cr1 |= SAI_XCR1_CKSTR; frcr |= SAI_XFRCR_FSPOL | SAI_XFRCR_FSOFF; break; case SND_SOC_DAIFMT_DSP_B: + cr1 |= SAI_XCR1_CKSTR; frcr |= SAI_XFRCR_FSPOL; break; default: