(This patch must be used AFTER the patch "V4L/DVB: mt9v011: Added exposure for
mt9v011")
The implementation of the gain calculation for this sensor is incorrect. It is
only working for the first 127 values.
The reason is, that the gain cannot be set directly by writing a value into the
gain registers of the sensor. The gain register work this way (see datasheet
page 24): bits 0 to 6 are called "initial gain". These are linear. But bits 7
and 8 ("analog multiplicative factors") and bits 9 and 10 ("digital
multiplicative factors") work completely different: Each of these bits increase
the gain by the factor 2. So if the bits 7-10 are 0011, 0110, 1100 or 0101 for
example, the gain from bits 0-6 is multiplied by 4. The order of the bits 7-10
is not important for the resulting gain. (But there are some recommended values
for low noise)
The current driver doesn't do this correctly: If the current gain is 000 0111
1111 (127) and the gain is increased by 1, you would expect the image to become
brighter. But the image is completly dark, because the new gain is 000 1000
0000 (128). This means: Initial gain of 0, multiplied by 2. The result is 0.
This patch adds a new function which does the gain calculation and also fixes
the same bug for red_balance and blue_balance. Additionally, the driver follows
the recommendation from the datasheet, which says, that the gain should always
be above 0x0020.
Signed-off-by: Johannes Obermaier <johannes.oberma...@gmail.com>
---
drivers/media/video/mt9v011.c | 63 +++++++++++++++++++++++++++++++++-------
1 files changed, 52 insertions(+), 11 deletions(-)
diff --git a/drivers/media/video/mt9v011.c b/drivers/media/video/mt9v011.c
index fbbd018..893a8b8 100644
--- a/drivers/media/video/mt9v011.c
+++ b/drivers/media/video/mt9v011.c
@@ -54,7 +54,7 @@ static struct v4l2_queryctrl mt9v011_qctrl[] = {
.type = V4L2_CTRL_TYPE_INTEGER,
.name = "Gain",
.minimum = 0,
- .maximum = (1 << 10) - 1,
+ .maximum = (1 << 12) - 1 - 0x0020,
.step = 1,
.default_value = 0x0020,
.flags = 0,
@@ -114,7 +114,8 @@ struct mt9v011 {
unsigned hflip:1;
unsigned vflip:1;
- u16 global_gain, exposure, red_bal, blue_bal;
+ u16 global_gain, exposure;
+ s16 red_bal, blue_bal;
};
static inline struct mt9v011 *to_mt9v011(struct v4l2_subdev *sd)
@@ -189,25 +190,65 @@ static const struct i2c_reg_value mt9v011_init_default[]
= {
{ R07_MT9V011_OUT_CTRL, 0x0002 }, /* chip enable */
};
+
+static u16 calc_mt9v011_gain(s16 lineargain)
+{
+
+ u16 digitalgain = 0;
+ u16 analogmult = 0;
+ u16 analoginit = 0;
+
+ if (lineargain < 0)
+ lineargain = 0;
+
+ /* recommended minimum */
+ lineargain += 0x0020;
+
+ if (lineargain > 2047)
+ lineargain = 2047;
+
+ if (lineargain > 1023) {
+ digitalgain = 3;
+ analogmult = 3;
+ analoginit = lineargain / 16;
+ } else if (lineargain > 511) {
+ digitalgain = 1;
+ analogmult = 3;
+ analoginit = lineargain / 8;
+ } else if (lineargain > 255) {
+ analogmult = 3;
+ analoginit = lineargain / 4;
+ } else if (lineargain > 127) {
+ analogmult = 1;
+ analoginit = lineargain / 2;
+ } else
+ analoginit = lineargain;
+
+ return analoginit + (analogmult << 7) + (digitalgain << 9);
+
+}
+
static void set_balance(struct v4l2_subdev *sd)
{
struct mt9v011 *core = to_mt9v011(sd);
- u16 green1_gain, green2_gain, blue_gain, red_gain;
+ u16 green_gain, blue_gain, red_gain;
u16 exposure;
+ s16 bal;
exposure = core->exposure;
- green1_gain = core->global_gain;
- green2_gain = core->global_gain;
+ green_gain = calc_mt9v011_gain(core->global_gain);
- blue_gain = core->global_gain +
- core->global_gain * core->blue_bal / (1 << 9);
+ bal = core->global_gain;
+ bal += (core->blue_bal * core->global_gain / (1 << 7));
+ blue_gain = calc_mt9v011_gain(bal);
- red_gain = core->global_gain +
- core->global_gain * core->blue_bal / (1 << 9);
+ bal = core->global_gain;
+ bal += (core->red_bal * core->global_gain / (1 << 7));
+ red_gain = calc_mt9v011_gain(bal);
- mt9v011_write(sd, R2B_MT9V011_GREEN_1_GAIN, green1_gain);
- mt9v011_write(sd, R2E_MT9V011_GREEN_2_GAIN, green1_gain);
+ mt9v011_write(sd, R2B_MT9V011_GREEN_1_GAIN, green_gain);
+ mt9v011_write(sd, R2E_MT9V011_GREEN_2_GAIN, green_gain);
mt9v011_write(sd, R2C_MT9V011_BLUE_GAIN, blue_gain);
mt9v011_write(sd, R2D_MT9V011_RED_GAIN, red_gain);
mt9v011_write(sd, R09_MT9V011_SHUTTER_WIDTH, exposure);
--
1.6.4.2
--
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