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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Umang Jain <umang.jain@ideasonboard.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Dave Stevenson <dave.stevenson@raspberrypi.com>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
	Sasha Levin <sashal@kernel.org>,
	linux-media@vger.kernel.org
Subject: [PATCH AUTOSEL 5.10 074/176] media: imx258: Limit the max analogue gain to 480
Date: Thu,  9 Sep 2021 07:49:36 -0400	[thread overview]
Message-ID: <20210909115118.146181-74-sashal@kernel.org> (raw)
In-Reply-To: <20210909115118.146181-1-sashal@kernel.org>

From: Umang Jain <umang.jain@ideasonboard.com>

[ 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>
---
 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 c0a691a73ec9..e6104ee97ed2 100644
--- a/drivers/media/i2c/imx258.c
+++ b/drivers/media/i2c/imx258.c
@@ -46,7 +46,7 @@
 /* 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
 
-- 
2.30.2


  parent reply	other threads:[~2021-09-09 13:46 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20210909115118.146181-1-sashal@kernel.org>
2021-09-09 11:48 ` [PATCH AUTOSEL 5.10 004/176] media: dib8000: rewrite the init prbs logic Sasha Levin
2021-09-09 11:48 ` [PATCH AUTOSEL 5.10 033/176] media: hantro: vp8: Move noisy WARN_ON to vpu_debug Sasha Levin
2021-09-09 11:48 ` [PATCH AUTOSEL 5.10 034/176] media: platform: stm32: unprepare clocks at handling errors in probe Sasha Levin
2021-09-09 11:48 ` [PATCH AUTOSEL 5.10 035/176] media: atomisp: Fix runtime PM imbalance in atomisp_pci_probe Sasha Levin
2021-09-09 11:48 ` [PATCH AUTOSEL 5.10 036/176] media: atomisp: pci: fix error return code in atomisp_pci_probe() Sasha Levin
2021-09-09 11:49 ` [PATCH AUTOSEL 5.10 073/176] media: imx258: Rectify mismatch of VTS value Sasha Levin
2021-09-09 11:49 ` Sasha Levin [this message]
2021-09-09 11:49 ` [PATCH AUTOSEL 5.10 075/176] media: v4l2-dv-timings.c: fix wrong condition in two for-loops Sasha Levin
2021-09-09 11:49 ` [PATCH AUTOSEL 5.10 076/176] media: TDA1997x: fix tda1997x_query_dv_timings() return value Sasha Levin
2021-09-09 11:49 ` [PATCH AUTOSEL 5.10 077/176] media: tegra-cec: Handle errors of clk_prepare_enable() Sasha Levin

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