media: imx290: Add module parameter to allow selection of HCG mode

The sensor has Low Conversion Gain (HCG) and High Conversion Gain (HCG)
modes, with the supposedly the HCG mode having better noise performance
at high gains.

As this parameter changes the gain range of the sensor, it isn't
possible to make this an automatic property, and there is no
suitable V4L2 control to set it, so just add it as a module parameter.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

Author: 6by9

drivers/media/i2c/imx290.c

@@ -13,6 +13,7 @@
 #include <linux/gpio/consumer.h>
 #include <linux/i2c.h>
 #include <linux/module.h>
+#include <linux/moduleparam.h>
 #include <linux/of.h>
 #include <linux/pm_runtime.h>
 #include <linux/regmap.h>
@@ -41,6 +42,9 @@
 #define IMX290_WINMODE_720P				(1 << 4)
 #define IMX290_WINMODE_CROP				(4 << 4)
 #define IMX290_FR_FDG_SEL				CCI_REG8(0x3009)
+#define IMX290_FDG_HCG					BIT(4)
+#define IMX290_FRSEL_60FPS				BIT(0)
+#define IMX290_FDG_LCG					0
 #define IMX290_BLKLEVEL					CCI_REG16_LE(0x300a)
 #define IMX290_GAIN					CCI_REG8(0x3014)
 #define IMX290_VMAX					CCI_REG24_LE(0x3018)
@@ -162,6 +166,10 @@
 
 #define IMX290_NUM_SUPPLIES				3
 
+static bool hcg_mode;
+module_param(hcg_mode, bool, 0664);
+MODULE_PARM_DESC(hcg_mode, "Enable HCG mode");
+
 enum imx290_colour_variant {
 	IMX290_VARIANT_COLOUR,
 	IMX290_VARIANT_MONO,
@@ -697,7 +705,8 @@ static int imx290_set_data_lanes(struct imx290 *imx290)
 		  &ret);
 	cci_write(imx290->regmap, IMX290_CSI_LANE_MODE, imx290->nlanes - 1,
 		  &ret);
-	cci_write(imx290->regmap, IMX290_FR_FDG_SEL, 0x01, &ret);
+	cci_write(imx290->regmap, IMX290_FR_FDG_SEL, IMX290_FRSEL_60FPS |
+		  (hcg_mode ? IMX290_FDG_HCG : IMX290_FDG_LCG), &ret);
 
 	return ret;
 }