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

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

[David Carlier]

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

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

[Jacopo Mondi]

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
>