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media: imx258: Limit the max analogue gain to 480

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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>
This commit is contained in:
Umang Jain 2021-07-23 13:22:33 +02:00 committed by Mauro Carvalho Chehab
parent 51f93add36
commit f809665ee7
1 changed files with 1 additions and 1 deletions
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2
drivers/media/i2c/imx258.c
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@ -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