[PATCH v3 6/6] media: imx335: Limit analogue gain value

From: Umang Jain
Date: Thu Mar 21 2024 - 07:15:09 EST


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@xxxxxxxxxxxxxxxx>
Reviewed-by: Kieran Bingham <kieran.bingham@xxxxxxxxxxxxxxxx>
Reviewed-by: Tommaso Merciai <tomm.merciai@xxxxxxxxx>
---
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 10a09830dbd6..9eb8f70836fd 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