On 08/05/2024 09:02, Jacopo Mondi wrote:
Hi Bryan
On Mon, May 06, 2024 at 11:38:26PM GMT, Bryan O'Donoghue wrote:
Currently we have the following algorithm to calculate what value should be
written to the exposure control of imx412.
lpfr = imx412->vblank + imx412->cur_mode->height;
shutter = lpfr - exposure;
The 'shutter' value is given to IMX412_REG_EXPOSURE_CIT however, the above
algorithm will result in the value given to IMX412_REG_EXPOSURE_CIT
decreasing as the requested exposure value from user-space goes up.
e.g.
[ 2255.713989] imx412 20-001a: Received exp 1608, analog gain 0
[ 2255.714002] imx412 20-001a: Set exp 1608, analog gain 0, shutter 1938, lpfr 3546
[ 2256.302770] imx412 20-001a: Received exp 2586, analog gain 100
[ 2256.302800] imx412 20-001a: Set exp 2586, analog gain 100, shutter 960, lpfr 3546
[ 2256.753755] imx412 20-001a: Received exp 3524, analog gain 110
[ 2256.753772] imx412 20-001a: Set exp 3524, analog gain 110, shutter 22, lpfr 3546
This behaviour results in the image having less exposure as the requested
exposure value from user-space increases.
Other sensor drivers such as ov5675, imx218, hid556 and others take the
requested exposure value and directly.
has the phrase been truncated or is it me reading it wrong ?
Sod's law says no matter how many times you send yourself a patch before
sending it to LKML you'll find a typo ~ 2 seconds after reading your
patch on LKML.
Looking at the range of imx sensors, it appears this particular error has
been replicated a number of times but, I haven't so far really drilled into
each sensor.
Ouch, what other driver have the same issue ?
So without data sheet or sensor its hard to say if these are correct or
incorrect, it's the same basic calculation though.
drivers/media/i2c/imx334.c::imx334_update_exp_gain()
lpfr = imx334->vblank + imx334->cur_mode->height;
shutter = lpfr - exposure;
ret = imx334_write_reg(imx334, IMX334_REG_SHUTTER, 3, shutter);
drivers/media/i2c/imx335.c::imx335_update_exp_gain()
lpfr = imx335->vblank + imx335->cur_mode->height;
shutter = lpfr - exposure;
ret = imx335_write_reg(imx335, IMX334_REG_SHUTTER, 3, shutter);
Looking again I'm inclined to believe the imx334/imx335 stuff is
probably correct for those sensors, got copied to imx412/imx577 and
misapplied to the EXPOSURE control in imx412.
- ret = imx412_write_reg(imx412, IMX412_REG_EXPOSURE_CIT, 2, shutter);
+ ret = imx412_write_reg(imx412, IMX412_REG_EXPOSURE_CIT, 2, exposure);
No datasheet here, can you confirm the IMX412_REG_EXPOSURE_CIT
register is actually in lines ?
Looks like.
From downstream "coarseIntgTimeAddr"
imx577_sensor.xml
<coarseIntgTimeAddr>0x0202</coarseIntgTimeAddr>
imx586/imx586_sensor.cpp
pRegSettingsInfo->regSetting[regCount].registerAddr =
pExposureData->pRegInfo->coarseIntgTimeAddr + 1;
pRegSettingsInfo->regSetting[regCount].registerData = (lineCount & 0xFF);
Apart from that, as the CID_EXPOSURE control limit are correctly
updated when a new VBLANK is set by taking into account the exposure
margins, I think writing the control value to the register is the
right thing to do (if the register is in lines of course)
Reviewed-by: Jacopo Mondi <jacopo.mondi@xxxxxxxxxxxxxxxx>
Thanks
j
If that's good enough I'll fix the typo and apply your RB.
---
bod
