Re: [PATCH] media: mali-c55: Fix AEXP IHIST disable bit shift

[Jacopo Mondi <jacopo.mondi@ideasonboard.com>]

Hi David

On Tue, Jun 09, 2026 at 06:32:31AM +0100, David Carlier wrote:
> The post-Iridix auto-exposure histogram disable bit in
> MALI_C55_REG_METERING_CONFIG is bit 16, but MALI_C55_AEXP_IHIST_DISABLE
> was defined with a shift of 12, copied from the AEXP_HIST definition
> above it. As the value is masked with the BIT(16) disable mask when it
> is programmed, the result is always zero and the disable bit is never
> set. The IHIST can therefore never be disabled, neither at ISP init nor
> via a parameters block flagged V4L2_ISP_PARAMS_FL_BLOCK_DISABLE, and the
> hardware keeps producing histogram statistics that userspace believes
> are switched off.
>
> Use a shift of 16 so the disable request takes effect.
>
> Fixes: d5f281f3dd29 ("media: mali-c55: Add Mali-C55 ISP driver")
> Cc: stable@vger.kernel.org
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: David Carlier <devnexen@gmail.com>
> ---
>  drivers/media/platform/arm/mali-c55/mali-c55-registers.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-registers.h b/drivers/media/platform/arm/mali-c55/mali-c55-registers.h
> index f098effde..4cd13b702 100644
> --- a/drivers/media/platform/arm/mali-c55/mali-c55-registers.h
> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-registers.h
> @@ -173,7 +173,7 @@ enum mali_c55_interrupts {
>  #define MALI_C55_AEXP_HIST_SWITCH_MASK			GENMASK(14, 13)
>  #define MALI_C55_AEXP_HIST_SWITCH(x)			((x) << 13)
>  #define MALI_C55_AEXP_IHIST_DISABLE_MASK		BIT(16)
> -#define MALI_C55_AEXP_IHIST_DISABLE			(0x01 << 12)
> +#define MALI_C55_AEXP_IHIST_DISABLE			(0x01 << 16)

Thanks, this indeed was a bad copy and paste I presume
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>

>  #define MALI_C55_AEXP_SRC_MASK				BIT(24)
>
>  #define MALI_C55_REG_TPG_CH0				0x18ed8
> --
> 2.53.0
>