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([213.192.89.162]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-66e034c9c47sm4815194a12.29.2026.04.08.01.44.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Apr 2026 01:44:37 -0700 (PDT) From: Tomasz Merta To: alsa-devel@alsa-project.org Cc: olivier.moysan@foss.st.com, arnaud.pouliquen@foss.st.com, lgirdwood@gmail.com, broonie@kernel.org, perex@perex.cz, tiwai@suse.com, mcoquelin.stm32@gmail.com, alexandre.torgue@foss.st.com, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Tomasz Merta , Tomasz Merta Subject: [PATCH] Subject: ASoC stm32_sai: fix incorrect BCLK polarity for DSP_A/B, LEFT_J Date: Wed, 8 Apr 2026 10:40:56 +0200 Message-Id: <20260408084056.20588-1-tommerta@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Tomasz Merta 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 --- sound/soc/stm/stm32_sai_sub.c | 3 +++ 1 file changed, 3 insertions(+) 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: -- 2.34.1