On Tue Jun 2 19:53:05 2026 +0100, David Carlier wrote:
> The 15x15 AEC histogram metering grid has 225 per-zone weights, packed
> by userspace as a u8 array. The driver writes the first 56 registers
> (zones 0 through 223) in a loop, then handles the final register on its
> own to keep static analysers from flagging the array access.
>
> That separate path computes the address and value for the 225th weight
> (the bottom-right zone) but never issues the register write, so the zone
> keeps its stale or default weight. Any non-default weight userspace sets
> for the last zone is silently ignored, skewing auto-exposure metering.
> Both the AEXP_HIST_WEIGHTS and AEXP_IHIST_WEIGHTS blocks are affected as
> they share this handler.
>
> Issue the missing write, masking the value as the loop does.
>
> Fixes: 01535ea08674 ("media: platform: Add mali-c55 parameters video node")
> Cc: [email protected]
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: David Carlier <[email protected]>
> Reviewed-by: Jacopo Mondi <[email protected]>
> Reviewed-by: Daniel Scally <[email protected]>
> Signed-off-by: Hans Verkuil <[email protected]>
Patch committed.
Thanks,
Hans Verkuil
drivers/media/platform/arm/mali-c55/mali-c55-params.c | 1 +
1 file changed, 1 insertion(+)
---
diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-params.c
b/drivers/media/platform/arm/mali-c55/mali-c55-params.c
index de0e9d898db7..33e2232ec8f5 100644
--- a/drivers/media/platform/arm/mali-c55/mali-c55-params.c
+++ b/drivers/media/platform/arm/mali-c55/mali-c55-params.c
@@ -212,6 +212,7 @@ mali_c55_params_aexp_hist_weights(struct mali_c55 *mali_c55,
val = params->zone_weights[MALI_C55_MAX_ZONES - 1];
addr = base + MALI_C55_AEXP_HIST_ZONE_WEIGHTS_OFFSET + (4 * 56);
+ mali_c55_ctx_write(mali_c55, addr, val &
MALI_C55_AEXP_HIST_ZONE_WEIGHT_MASK);
}
static void mali_c55_params_digital_gain(struct mali_c55 *mali_c55,
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