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

[David Carlier <devnexen@gmail.com>]

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@vger.kernel.org
Signed-off-by: David Carlier <devnexen@gmail.com>
---

Notes:
    v2: Define the macro as a 64-bit constant (BIT_ULL) instead of casting
        each multiplication, per Dan's review.

 drivers/media/platform/arm/mali-c55/mali-c55-resizer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-resizer.c b/drivers/media/platform/arm/mali-c55/mali-c55-resizer.c
index c4f46651d..6706939b4 100644
--- a/drivers/media/platform/arm/mali-c55/mali-c55-resizer.c
+++ b/drivers/media/platform/arm/mali-c55/mali-c55-resizer.c
@@ -15,7 +15,7 @@
 #include "mali-c55-registers.h"
 
 /* Scaling factor in Q4.20 format. */
-#define MALI_C55_RSZ_SCALER_FACTOR	(1U << 20)
+#define MALI_C55_RSZ_SCALER_FACTOR	BIT_ULL(20)
 
 #define MALI_C55_RSZ_COEFS_BANKS	8
 #define MALI_C55_RSZ_COEFS_ENTRIES	64
-- 
2.53.0