linux-kernel - [PATCH v4 6/6] media: imx335: Limit analogue gain value

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Date: Tue,  2 Apr 2024 19:39:24 +0530
From: Umang Jain <umang.jain@...asonboard.com>
To: linux-media@...r.kernel.org
Cc: Alexander Shiyan <eagle.alexander923@...il.com>,
	Kieran Bingham <kieran.bingham@...asonboard.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	open list <linux-kernel@...r.kernel.org>,
	Dave Stevenson <dave.stevenson@...pberrypi.com>,
	Umang Jain <umang.jain@...asonboard.com>,
	Tommaso Merciai <tomm.merciai@...il.com>
Subject: [PATCH v4 6/6] media: imx335: Limit analogue gain value

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@...asonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@...asonboard.com>
Reviewed-by: Tommaso Merciai <tomm.merciai@...il.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 dfc24783dc34..aed3efa9f590 100644
--- a/drivers/media/i2c/imx335.c
+++ b/drivers/media/i2c/imx335.c
@@ -52,7 +52,7 @@
 /* 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
 
@@ -1175,6 +1175,14 @@ 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