[PATCH 0/2] ASoC: stm32: sai: fix kernel rate configuration

[PATCH 0/2] ASoC: stm32: sai: fix kernel rate configuration

[Olivier Moysan]

This patchset adds some checks on kernel minimum rate requirements.
This avoids potential clock rate misconfiguration, when setting the
kernel frequency on STM32MP2 SoCs.

Olivier Moysan (2):
  ASoC: stm32: sai: skip useless iterations on kernel rate loop
  ASoC: stm32: sai: add a check on minimal kernel frequency

 sound/soc/stm/stm32_sai_sub.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)


base-commit: a9bfaf85aaf2dabf541eb7a4895db025d6d8eb1c
-- 
2.25.1

[PATCH 1/2] ASoC: stm32: sai: skip useless iterations on kernel rate loop

[Olivier Moysan]

the frequency of the kernel clock must be greater than or equal to the
bitclock rate. When searching for a convenient kernel clock rate in
stm32_sai_set_parent_rate() function, it is useless to continue the loop
below bitclock rate, as it will result in a invalid kernel clock rate.
Change the loop output condition.

Fixes: b1d2e4067dc6 ("ASoC: stm32: sai: add stm32mp25 support")
Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
---
 sound/soc/stm/stm32_sai_sub.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/sound/soc/stm/stm32_sai_sub.c b/sound/soc/stm/stm32_sai_sub.c
index e8c1abf1ae0a..4d018b4bc3f0 100644
--- a/sound/soc/stm/stm32_sai_sub.c
+++ b/sound/soc/stm/stm32_sai_sub.c
@@ -409,11 +409,11 @@ static int stm32_sai_set_parent_rate(struct stm32_sai_sub_data *sai,
 				     unsigned int rate)
 {
 	struct platform_device *pdev = sai->pdev;
-	unsigned int sai_ck_rate, sai_ck_max_rate, sai_curr_rate, sai_new_rate;
+	unsigned int sai_ck_rate, sai_ck_max_rate, sai_ck_min_rate, sai_curr_rate, sai_new_rate;
 	int div, ret;
 
 	/*
-	 * Set maximum expected kernel clock frequency
+	 * Set minimum and maximum expected kernel clock frequency
 	 * - mclk on or spdif:
 	 *   f_sai_ck = MCKDIV * mclk-fs * fs
 	 *   Here typical 256 ratio is assumed for mclk-fs
@@ -423,13 +423,16 @@ static int stm32_sai_set_parent_rate(struct stm32_sai_sub_data *sai,
 	 *   Set constraint MCKDIV * FRL <= 256, to ensure MCKDIV is in available range
 	 *   f_sai_ck = sai_ck_max_rate * pow_of_two(FRL) / 256
 	 */
+	sai_ck_min_rate = rate * 256;
 	if (!(rate % SAI_RATE_11K))
 		sai_ck_max_rate = SAI_MAX_SAMPLE_RATE_11K * 256;
 	else
 		sai_ck_max_rate = SAI_MAX_SAMPLE_RATE_8K * 256;
 
-	if (!sai->sai_mclk && !STM_SAI_PROTOCOL_IS_SPDIF(sai))
+	if (!sai->sai_mclk && !STM_SAI_PROTOCOL_IS_SPDIF(sai)) {
+		sai_ck_min_rate = rate * sai->fs_length;
 		sai_ck_max_rate /= DIV_ROUND_CLOSEST(256, roundup_pow_of_two(sai->fs_length));
+	}
 
 	/*
 	 * Request exclusivity, as the clock is shared by SAI sub-blocks and by
@@ -472,7 +475,7 @@ static int stm32_sai_set_parent_rate(struct stm32_sai_sub_data *sai,
 		/* Try a lower frequency */
 		div++;
 		sai_ck_rate = sai_ck_max_rate / div;
-	} while (sai_ck_rate > rate);
+	} while (sai_ck_rate >= sai_ck_min_rate);
 
 	/* No accurate rate found */
 	dev_err(&pdev->dev, "Failed to find an accurate rate");
-- 
2.25.1

Re: [PATCH 1/2] ASoC: stm32: sai: skip useless iterations on kernel rate loop

[Mark Brown]

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On Wed, Apr 30, 2025 at 06:52:08PM +0200, Olivier Moysan wrote:

> Fixes: b1d2e4067dc6 ("ASoC: stm32: sai: add stm32mp25 support")

This commit isn't in mainline, I think you meant 2cfe1ff22555.

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[PATCH 2/2] ASoC: stm32: sai: add a check on minimal kernel frequency

[Olivier Moysan]

On MP2 SoCs SAI kernel clock rate is managed through
stm32_sai_set_parent_rate() function.
If the kernel clock rate was set previously to a low frequency, this
frequency may be too low to support the newly requested audio stream rate.
However the stm32_sai_rate_accurate() will only check accuracy against
the maximum kernel clock rate. The function will return leaving the kernel
clock rate unchanged.
Add a check on minimal frequency requirement, to avoid this.

Fixes: b1d2e4067dc6 ("ASoC: stm32: sai: add stm32mp25 support")
Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
---
 sound/soc/stm/stm32_sai_sub.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/sound/soc/stm/stm32_sai_sub.c b/sound/soc/stm/stm32_sai_sub.c
index 4d018b4bc3f0..bf5299ba11c3 100644
--- a/sound/soc/stm/stm32_sai_sub.c
+++ b/sound/soc/stm/stm32_sai_sub.c
@@ -447,7 +447,10 @@ static int stm32_sai_set_parent_rate(struct stm32_sai_sub_data *sai,
 	 * return immediately.
 	 */
 	sai_curr_rate = clk_get_rate(sai->sai_ck);
-	if (stm32_sai_rate_accurate(sai_ck_max_rate, sai_curr_rate))
+	dev_dbg(&pdev->dev, "kernel clock rate: min [%u], max [%u], current [%u]",
+		sai_ck_min_rate, sai_ck_max_rate, sai_curr_rate);
+	if (stm32_sai_rate_accurate(sai_ck_max_rate, sai_curr_rate) &&
+	    sai_curr_rate >= sai_ck_min_rate)
 		return 0;
 
 	/*
-- 
2.25.1

Re: [PATCH 0/2] ASoC: stm32: sai: fix kernel rate configuration

[Mark Brown]

On Wed, 30 Apr 2025 18:52:07 +0200, Olivier Moysan wrote:
> This patchset adds some checks on kernel minimum rate requirements.
> This avoids potential clock rate misconfiguration, when setting the
> kernel frequency on STM32MP2 SoCs.
> 
> Olivier Moysan (2):
>   ASoC: stm32: sai: skip useless iterations on kernel rate loop
>   ASoC: stm32: sai: add a check on minimal kernel frequency
> 
> [...]

Applied to

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

Thanks!

[1/2] ASoC: stm32: sai: skip useless iterations on kernel rate loop
      commit: edea92770a3b6454dc796fc5436a3315bb402181
[2/2] ASoC: stm32: sai: add a check on minimal kernel frequency
      commit: cce34d113e2a592806abcdc02c7f8513775d8b20

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