linux-kernel - [PATCH v3 19/23] media: atmel: atmel-isc-base: clamp wb gain coefficients

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Message-ID: <20211213134940.324266-20-eugen.hristev@microchip.com>
Date:   Mon, 13 Dec 2021 15:49:36 +0200
From:   Eugen Hristev <eugen.hristev@...rochip.com>
To:     <linux-media@...r.kernel.org>, <robh+dt@...nel.org>,
        <jacopo@...ndi.org>, <laurent.pinchart@...asonboard.com>,
        <sakari.ailus@....fi>
CC:     <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <nicolas.ferre@...rochip.com>,
        "Eugen Hristev" <eugen.hristev@...rochip.com>
Subject: [PATCH v3 19/23] media: atmel: atmel-isc-base: clamp wb gain coefficients

White balance computed gains can overflow above the 13 bits hardware
coefficient that can be used, in some specific scenarios like a subexposure
from the sensor when the image is mostly black.
In this case the computed gain has to be clamped to the maximum value
allowed by the hardware.

Signed-off-by: Eugen Hristev <eugen.hristev@...rochip.com>
---
 drivers/media/platform/atmel/atmel-isc-base.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/media/platform/atmel/atmel-isc-base.c b/drivers/media/platform/atmel/atmel-isc-base.c
index f1f1019f9d82..31c8e3029eee 100644
--- a/drivers/media/platform/atmel/atmel-isc-base.c
+++ b/drivers/media/platform/atmel/atmel-isc-base.c
@@ -1415,6 +1415,10 @@ static void isc_wb_update(struct isc_ctrls *ctrls)
 		/* multiply both gains and adjust for decimals */
 		ctrls->gain[c] = s_gain[c] * gw_gain[c];
 		ctrls->gain[c] >>= 9;
+
+		/* make sure we are not out of range */
+		ctrls->gain[c] = clamp_val(ctrls->gain[c], 0, GENMASK(12, 0));
+
 		v4l2_dbg(1, debug, &isc->v4l2_dev,
 			 "isc wb: component %d, final gain %u\n",
 			 c, ctrls->gain[c]);
-- 
2.25.1