Re: [PATCH v2] media: mali-c55: Fix scaler factor overflow for large crop sizes

[Linus Walleij]

On Thu, Jun 18, 2026 at 9:53 PM David Carlier <devnexen@xxxxxxxxx> wrote:

> The horizontal and vertical scaling factors multiply the crop dimensions
> by MALI_C55_RSZ_SCALER_FACTOR, a Q4.20 factor of (1 << 20). Both operands
> are 32-bit, so the multiplication wraps before the result is stored in
> the u64 scale variables. For any crop dimension of 4096 or more (the
> maximum is 8192) the value overflows; an 8192 to 4096 downscale yields a
> TINC of zero, so the scaler never advances and the output is corrupted.
>
> Define MALI_C55_RSZ_SCALER_FACTOR as a 64-bit constant so the
> multiplication is performed in 64-bit.
>
> Fixes: d5f281f3dd29 ("media: mali-c55: Add Mali-C55 ISP driver")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: David Carlier <devnexen@xxxxxxxxx>

LGTM
Reviewed-by: Linus Walleij <linusw@xxxxxxxxxx>

Yours,
Linus Walleij