media: ov5675: use group write to update digital gain

MWB gain register are used to set gain for each mwb channel mannually.
However, it will involve some artifacts at low light environment as gain
cannot be applied to each channel synchronously. Update the driver to use
group write for digital gain to make the sure RGB digital gain be applied
together at frame boundary.

Signed-off-by: Bingbu Cao <bingbu.cao@intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

diff --git a/drivers/media/i2c/ov5675.c b/drivers/media/i2c/ov5675.c
index 00925850fa7cac357ed30c90171d9db65a0208a5..82ba9f56baec83f7cb61f15ca51d322b4bd62f51 100644 (file)
--- a/drivers/media/i2c/ov5675.c
+++ b/drivers/media/i2c/ov5675.c
@@ -50,14 +50,21 @@
 #define        OV5675_ANAL_GAIN_STEP           1
 
 /* Digital gain controls from sensor */
+#define OV5675_REG_DIGITAL_GAIN                0x350a
 #define OV5675_REG_MWB_R_GAIN          0x5019
 #define OV5675_REG_MWB_G_GAIN          0x501b
 #define OV5675_REG_MWB_B_GAIN          0x501d
-#define OV5675_DGTL_GAIN_MIN           0
+#define OV5675_DGTL_GAIN_MIN           1024
 #define OV5675_DGTL_GAIN_MAX           4095
 #define OV5675_DGTL_GAIN_STEP          1
 #define OV5675_DGTL_GAIN_DEFAULT       1024
 
+/* Group Access */
+#define OV5675_REG_GROUP_ACCESS                0x3208
+#define OV5675_GROUP_HOLD_START                0x0
+#define OV5675_GROUP_HOLD_END          0x10
+#define OV5675_GROUP_HOLD_LAUNCH       0xa0
+
 /* Test Pattern Control */
 #define OV5675_REG_TEST_PATTERN                0x4503
 #define OV5675_TEST_PATTERN_ENABLE     BIT(7)
@@ -587,6 +594,12 @@ static int ov5675_update_digital_gain(struct ov5675 *ov5675, u32 d_gain)
 {
        int ret;
 
+       ret = ov5675_write_reg(ov5675, OV5675_REG_GROUP_ACCESS,
+                              OV5675_REG_VALUE_08BIT,
+                              OV5675_GROUP_HOLD_START);
+       if (ret)
+               return ret;
+
        ret = ov5675_write_reg(ov5675, OV5675_REG_MWB_R_GAIN,
                               OV5675_REG_VALUE_16BIT, d_gain);
        if (ret)
@@ -597,8 +610,21 @@ static int ov5675_update_digital_gain(struct ov5675 *ov5675, u32 d_gain)
        if (ret)
                return ret;
 
-       return ov5675_write_reg(ov5675, OV5675_REG_MWB_B_GAIN,
-                               OV5675_REG_VALUE_16BIT, d_gain);
+       ret = ov5675_write_reg(ov5675, OV5675_REG_MWB_B_GAIN,
+                              OV5675_REG_VALUE_16BIT, d_gain);
+       if (ret)
+               return ret;
+
+       ret = ov5675_write_reg(ov5675, OV5675_REG_GROUP_ACCESS,
+                              OV5675_REG_VALUE_08BIT,
+                              OV5675_GROUP_HOLD_END);
+       if (ret)
+               return ret;
+
+       ret = ov5675_write_reg(ov5675, OV5675_REG_GROUP_ACCESS,
+                              OV5675_REG_VALUE_08BIT,
+                              OV5675_GROUP_HOLD_LAUNCH);
+       return ret;
 }
 
 static int ov5675_test_pattern(struct ov5675 *ov5675, u32 pattern)