From f3d1566d8c978fed1f6261b00af2a02aeba31676 Mon Sep 17 00:00:00 2001
From: Umang Jain <umang.jain@ideasonboard.com>
Date: Fri, 23 Jul 2021 13:22:33 +0200
Subject: [PATCH] media: imx258: Limit the max analogue gain to 480
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Git-commit: f809665ee75fff3f4ea8907f406a66d380aeb184
Patch-mainline: v5.15-rc1
References: stable-5.14.6

[ Upstream commit f809665ee75fff3f4ea8907f406a66d380aeb184 ]

The range for analog gain mentioned in the datasheet is [0, 480].
The real gain formula mentioned in the datasheet is:

	Gain = 512 / (512 – X)

Hence, values larger than 511 clearly makes no sense. The gain
register field is also documented to be of 9-bits in the datasheet.

Certainly, it is enough to infer that, the kernel driver currently
advertises an arbitrary analog gain max. Fix it by rectifying the
value as per the data sheet i.e. 480.

Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/media/i2c/imx258.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/i2c/imx258.c b/drivers/media/i2c/imx258.c
index 4e695096e5d0..81cdf37216ca 100644
--- a/drivers/media/i2c/imx258.c
+++ b/drivers/media/i2c/imx258.c
@@ -47,7 +47,7 @@
 /* Analog gain control */
 #define IMX258_REG_ANALOG_GAIN		0x0204
 #define IMX258_ANA_GAIN_MIN		0
-#define IMX258_ANA_GAIN_MAX		0x1fff
+#define IMX258_ANA_GAIN_MAX		480
 #define IMX258_ANA_GAIN_STEP		1
 #define IMX258_ANA_GAIN_DEFAULT		0x0
 
-- 
2.26.2