[PATCH v5 02/12] media: microchip-isc: fix WB offset and gain register field masking

[Balakrishnan Sambath <balakrishnan.s@microchip.com>]

ISC_WB_O_* and ISC_WB_G_* pack two 13-bit fields per register. Sign
extension from negative offsets corrupts the upper field. Mask both
fields to 13 bits before packing.

Fixes: 91b4e487b0c6 ("media: microchip: add ISC driver as Microchip ISC")
Cc: stable@vger.kernel.org
Signed-off-by: Balakrishnan Sambath <balakrishnan.s@microchip.com>
---
 .../media/platform/microchip/microchip-isc-base.c   | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/media/platform/microchip/microchip-isc-base.c b/drivers/media/platform/microchip/microchip-isc-base.c
index a7cdc743fda7..45b94f1e89d8 100644
--- a/drivers/media/platform/microchip/microchip-isc-base.c
+++ b/drivers/media/platform/microchip/microchip-isc-base.c
@@ -61,18 +61,23 @@ static inline void isc_update_awb_ctrls(struct isc_device *isc)
 
 	/* In here we set our actual hw pipeline config */
 
+	/*
+	 * Mask offset fields to 13 bits. Sign extension of negative s32
+	 * values would otherwise corrupt the adjacent field.
+	 */
 	regmap_write(isc->regmap, ISC_WB_O_RGR,
-		     ((ctrls->offset[ISC_HIS_CFG_MODE_R])) |
-		     ((ctrls->offset[ISC_HIS_CFG_MODE_GR]) << 16));
+		     ((u32)ctrls->offset[ISC_HIS_CFG_MODE_R] & GENMASK(12, 0)) |
+		     (((u32)ctrls->offset[ISC_HIS_CFG_MODE_GR] & GENMASK(12, 0)) << 16));
 	regmap_write(isc->regmap, ISC_WB_O_BGB,
-		     ((ctrls->offset[ISC_HIS_CFG_MODE_B])) |
-		     ((ctrls->offset[ISC_HIS_CFG_MODE_GB]) << 16));
+		     ((u32)ctrls->offset[ISC_HIS_CFG_MODE_B] & GENMASK(12, 0)) |
+		     (((u32)ctrls->offset[ISC_HIS_CFG_MODE_GB] & GENMASK(12, 0)) << 16));
+	/* Gains are 13-bit unsigned fields [12:0] and [28:16] */
 	regmap_write(isc->regmap, ISC_WB_G_RGR,
-		     ctrls->gain[ISC_HIS_CFG_MODE_R] |
-		     (ctrls->gain[ISC_HIS_CFG_MODE_GR] << 16));
+		     (ctrls->gain[ISC_HIS_CFG_MODE_R] & GENMASK(12, 0)) |
+		     ((ctrls->gain[ISC_HIS_CFG_MODE_GR] & GENMASK(12, 0)) << 16));
 	regmap_write(isc->regmap, ISC_WB_G_BGB,
-		     ctrls->gain[ISC_HIS_CFG_MODE_B] |
-		     (ctrls->gain[ISC_HIS_CFG_MODE_GB] << 16));
+		     (ctrls->gain[ISC_HIS_CFG_MODE_B] & GENMASK(12, 0)) |
+		     ((ctrls->gain[ISC_HIS_CFG_MODE_GB] & GENMASK(12, 0)) << 16));
 }
 
 static inline void isc_reset_awb_ctrls(struct isc_device *isc)

-- 
2.34.1