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From: Umang Jain <umang.jain@ideasonboard.com>
To: linux-media@vger.kernel.org
Cc: Alexander Shiyan <eagle.alexander923@gmail.com>,
	Kieran Bingham <kieran.bingham@ideasonboard.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	open list <linux-kernel@vger.kernel.org>,
	Umang Jain <umang.jain@ideasonboard.com>
Subject: [PATCH 5/5] media: imx335: Limit analogue gain value
Date: Wed,  6 Mar 2024 13:40:38 +0530
Message-ID: <20240306081038.212412-6-umang.jain@ideasonboard.com>
In-Reply-To: <20240306081038.212412-1-umang.jain@ideasonboard.com>
References: <20240306081038.212412-1-umang.jain@ideasonboard.com>
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The sensor gain (both analog and digital) are controlled by a
single gain value where:
- 0dB to 30dB correspond to analog gain
- 30.3dB to 72dB correspond to digital gain
(with 0.3dB step)

Hence, limit the analogue gain value to 100.
For digital gain, support can be added later if needed.

Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
---
 drivers/media/i2c/imx335.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/media/i2c/imx335.c b/drivers/media/i2c/imx335.c
index c00e0c2be3f3..701bd5318b45 100644
--- a/drivers/media/i2c/imx335.c
+++ b/drivers/media/i2c/imx335.c
@@ -45,7 +45,7 @@
 /* Analog gain control */
 #define IMX335_REG_AGAIN	CCI_REG8(0x30e8)
 #define IMX335_AGAIN_MIN	0
-#define IMX335_AGAIN_MAX	240
+#define IMX335_AGAIN_MAX	100
 #define IMX335_AGAIN_STEP	1
 #define IMX335_AGAIN_DEFAULT	0
 
@@ -1169,6 +1169,14 @@ static int imx335_init_controls(struct imx335 *imx335)
 					     IMX335_EXPOSURE_STEP,
 					     IMX335_EXPOSURE_DEFAULT);
 
+	/*
+	 * The sensor has an analog gain and a digital gain, both controlled
+	 * through a single gain value, expressed in 0.3dB increments. Values
+	 * from 0.0dB (0) to 30.0dB (100) apply analog gain only, higher values
+	 * up to 72.0dB (240) add further digital gain. Limit the range to
+	 * analog gain only, support for digital gain can be added separately
+	 * if needed.
+	 */
 	imx335->again_ctrl = v4l2_ctrl_new_std(ctrl_hdlr,
 					       &imx335_ctrl_ops,
 					       V4L2_CID_ANALOGUE_GAIN,
-- 
2.43.0