media: ov13858: Increase digital gain granularity, range

Previously, possible digital gains were just 1x, 2x and 4x. These
coarse gains were not sufficient in fine-tuning the image capture.

Now, digital gain range is [0, 16x] with each step 1/1024, default 1x.
This is achieved through OV13858 MWB R/G/B gain controls.

Signed-off-by: Chiranjeevi Rapolu <chiranjeevi.rapolu@intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/i2c/ov13858.c

@@ -77,13 +77,13 @@
 #define OV13858_ANA_GAIN_DEFAULT	0x80
 
 /* Digital gain control */
-#define OV13858_REG_DIGITAL_GAIN	0x350a
-#define OV13858_DGTL_GAIN_MASK		0xf3
-#define OV13858_DGTL_GAIN_SHIFT		2
-#define OV13858_DGTL_GAIN_MIN		1
-#define OV13858_DGTL_GAIN_MAX		4
-#define OV13858_DGTL_GAIN_STEP		1
-#define OV13858_DGTL_GAIN_DEFAULT	1
+#define OV13858_REG_B_MWB_GAIN		0x5100
+#define OV13858_REG_G_MWB_GAIN		0x5102
+#define OV13858_REG_R_MWB_GAIN		0x5104
+#define OV13858_DGTL_GAIN_MIN		0
+#define OV13858_DGTL_GAIN_MAX		16384	/* Max = 16 X */
+#define OV13858_DGTL_GAIN_DEFAULT	1024	/* Default gain = 1 X */
+#define OV13858_DGTL_GAIN_STEP		1	/* Each step = 1/1024 */
 
 /* Test Pattern Control */
 #define OV13858_REG_TEST_PATTERN	0x4503
@@ -1162,21 +1162,21 @@ static int ov13858_open(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
 static int ov13858_update_digital_gain(struct ov13858 *ov13858, u32 d_gain)
 {
 	int ret;
-	u32 val;
 
-	if (d_gain == 3)
-		return -EINVAL;
-
-	ret = ov13858_read_reg(ov13858, OV13858_REG_DIGITAL_GAIN,
-			       OV13858_REG_VALUE_08BIT, &val);
+	ret = ov13858_write_reg(ov13858, OV13858_REG_B_MWB_GAIN,
+				OV13858_REG_VALUE_16BIT, d_gain);
 	if (ret)
 		return ret;
 
-	val &= OV13858_DGTL_GAIN_MASK;
-	val |= (d_gain - 1) << OV13858_DGTL_GAIN_SHIFT;
+	ret = ov13858_write_reg(ov13858, OV13858_REG_G_MWB_GAIN,
+				OV13858_REG_VALUE_16BIT, d_gain);
+	if (ret)
+		return ret;
 
-	return ov13858_write_reg(ov13858, OV13858_REG_DIGITAL_GAIN,
-				 OV13858_REG_VALUE_08BIT, val);
+	ret = ov13858_write_reg(ov13858, OV13858_REG_R_MWB_GAIN,
+				OV13858_REG_VALUE_16BIT, d_gain);
+
+	return ret;
 }
 
 static int ov13858_enable_test_pattern(struct ov13858 *ov13858, u32 pattern)