[PATCH] ASoC: tegra: tegra210-mixer: Use div_u64() for 64-bit division

[PATCH] ASoC: tegra: tegra210-mixer: Use div_u64() for 64-bit division

[Rosen Penev]

A MIPS allmodconfig build with LLVM fails during modpost:

  ERROR: modpost: "__udivdi3"
  [sound/soc/tegra/snd-soc-tegra210-mixer.ko] undefined!

tegra210_mixer_configure_gain() divides a 64-bit BIT_ULL() value by the
fade duration. On 32-bit MIPS, clang emits a call to __udivdi3 for that
plain C division, but that compiler helper is not exported to modules.

Use div_u64() for the inverse duration calculation so the driver uses the
kernel's 64-bit division helper instead of emitting a compiler runtime
call.

Assisted-by: Codex:GPT-5.5
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 sound/soc/tegra/tegra210_mixer.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/sound/soc/tegra/tegra210_mixer.c b/sound/soc/tegra/tegra210_mixer.c
index f05617b5f433..bfdd457f740c 100644
--- a/sound/soc/tegra/tegra210_mixer.c
+++ b/sound/soc/tegra/tegra210_mixer.c
@@ -7,6 +7,7 @@
 #include <linux/clk.h>
 #include <linux/device.h>
 #include <linux/io.h>
+#include <linux/math64.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
@@ -157,8 +158,8 @@ static int tegra210_mixer_configure_gain(struct snd_soc_component *cmpnt,
 			if (i == DURATION_N3_ID)
 				val = mixer->duration[id];
 			else if (i == DURATION_INV_N3_ID)
-				val = (u32)(BIT_ULL(31 + TEGRA210_MIXER_PRESCALAR) /
-					    mixer->duration[id]);
+				val = div_u64(BIT_ULL(31 + TEGRA210_MIXER_PRESCALAR),
+					      mixer->duration[id]);
 			else
 				val = gain_params.duration[i];
 		}
-- 
2.54.0

Re: [PATCH] ASoC: tegra: tegra210-mixer: Use div_u64() for 64-bit division

[Mark Brown]

On Thu, 07 May 2026 16:21:31 -0700, Rosen Penev wrote:
> ASoC: tegra: tegra210-mixer: Use div_u64() for 64-bit division

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-7.2

Thanks!

[1/1] ASoC: tegra: tegra210-mixer: Use div_u64() for 64-bit division
      https://git.kernel.org/broonie/sound/c/04b8f96b1088

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

Re: [PATCH] ASoC: tegra: tegra210-mixer: Use div_u64() for 64-bit division

[Nathan Chancellor]

On Thu, May 07, 2026 at 04:21:31PM -0700, Rosen Penev wrote:
> A MIPS allmodconfig build with LLVM fails during modpost:
> 
>   ERROR: modpost: "__udivdi3"
>   [sound/soc/tegra/snd-soc-tegra210-mixer.ko] undefined!
> 
> tegra210_mixer_configure_gain() divides a 64-bit BIT_ULL() value by the
> fade duration. On 32-bit MIPS, clang emits a call to __udivdi3 for that
> plain C division, but that compiler helper is not exported to modules.
> 
> Use div_u64() for the inverse duration calculation so the driver uses the
> kernel's 64-bit division helper instead of emitting a compiler runtime
> call.
> 
> Assisted-by: Codex:GPT-5.5
> Signed-off-by: Rosen Penev <rosenp@gmail.com>

This is neither a Clang nor MIPS specific issue, it will happen with any
32-bit target, as Arnd's patch shows:

  https://lore.kernel.org/20260508080031.4064272-1-arnd@kernel.org/

Regardless, this is obviously the correct fix.

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
>  sound/soc/tegra/tegra210_mixer.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/soc/tegra/tegra210_mixer.c b/sound/soc/tegra/tegra210_mixer.c
> index f05617b5f433..bfdd457f740c 100644
> --- a/sound/soc/tegra/tegra210_mixer.c
> +++ b/sound/soc/tegra/tegra210_mixer.c
> @@ -7,6 +7,7 @@
>  #include <linux/clk.h>
>  #include <linux/device.h>
>  #include <linux/io.h>
> +#include <linux/math64.h>
>  #include <linux/mod_devicetable.h>
>  #include <linux/module.h>
>  #include <linux/platform_device.h>
> @@ -157,8 +158,8 @@ static int tegra210_mixer_configure_gain(struct snd_soc_component *cmpnt,
>  			if (i == DURATION_N3_ID)
>  				val = mixer->duration[id];
>  			else if (i == DURATION_INV_N3_ID)
> -				val = (u32)(BIT_ULL(31 + TEGRA210_MIXER_PRESCALAR) /
> -					    mixer->duration[id]);
> +				val = div_u64(BIT_ULL(31 + TEGRA210_MIXER_PRESCALAR),
> +					      mixer->duration[id]);
>  			else
>  				val = gain_params.duration[i];
>  		}
> -- 
> 2.54.0
> 

-- 
Cheers,
Nathan

Re: [PATCH] ASoC: tegra: tegra210-mixer: Use div_u64() for 64-bit division

[Thierry Reding]

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On Thu, May 07, 2026 at 04:21:31PM -0700, Rosen Penev wrote:
> A MIPS allmodconfig build with LLVM fails during modpost:
> 
>   ERROR: modpost: "__udivdi3"
>   [sound/soc/tegra/snd-soc-tegra210-mixer.ko] undefined!
> 
> tegra210_mixer_configure_gain() divides a 64-bit BIT_ULL() value by the
> fade duration. On 32-bit MIPS, clang emits a call to __udivdi3 for that
> plain C division, but that compiler helper is not exported to modules.
> 
> Use div_u64() for the inverse duration calculation so the driver uses the
> kernel's 64-bit division helper instead of emitting a compiler runtime
> call.
> 
> Assisted-by: Codex:GPT-5.5
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
>  sound/soc/tegra/tegra210_mixer.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)

Acked-by: Thierry Reding <treding@nvidia.com>

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