@@ -542,14 +542,13 @@ static int imx412_update_controls(struct imx412 *imx412,
*/
static int imx412_update_exp_gain(struct imx412 *imx412, u32 exposure, u32 gain)
{
- u32 lpfr, shutter;
+ u32 lpfr;
int ret;
lpfr = imx412->vblank + imx412->cur_mode->height;
- shutter = lpfr - exposure;
- dev_dbg(imx412->dev, "Set exp %u, analog gain %u, shutter %u, lpfr %u",
- exposure, gain, shutter, lpfr);
+ dev_dbg(imx412->dev, "Set exp %u, analog gain %u, lpfr %u",
+ exposure, gain, lpfr);
ret = imx412_write_reg(imx412, IMX412_REG_HOLD, 1, 1);
if (ret)
@@ -559,7 +558,7 @@ static int imx412_update_exp_gain(struct imx412 *imx412, u32 exposure, u32 gain)
if (ret)
goto error_release_group_hold;
- ret = imx412_write_reg(imx412, IMX412_REG_EXPOSURE_CIT, 2, shutter);
+ ret = imx412_write_reg(imx412, IMX412_REG_EXPOSURE_CIT, 2, exposure);
if (ret)
goto error_release_group_hold;
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 use the value directly. Take the example of the above cited sensor drivers and directly apply the requested exposure value from user-space. The 'lpfr' variable still functions as before but the 'shutter' variable can be dispensed with as a result. Once done a similar run of the test application requesting higher exposure looks like this, with 'exp' written directly to the sensor. [ 133.207884] imx412 20-001a: Received exp 1608, analog gain 0 [ 133.207899] imx412 20-001a: Set exp 1608, analog gain 0, lpfr 3546 [ 133.905309] imx412 20-001a: Received exp 2844, analog gain 100 [ 133.905344] imx412 20-001a: Set exp 2844, analog gain 100, lpfr 3546 [ 134.241705] imx412 20-001a: Received exp 3524, analog gain 110 [ 134.241775] imx412 20-001a: Set exp 3524, analog gain 110, lpfr 3546 The result is then setting the sensor exposure to lower values results in darker, less exposure images and vice versa with higher exposure values. Fixes: 9214e86c0cc1 ("media: i2c: Add imx412 camera sensor driver") Tested-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org> # qrb5165-rb5/imx577 Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com> Reviewed-by: Gjorgji Rosikopulos <quic_grosikop@quicinc.com> Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org> --- Using libcamera/SoftISP on a Qualcomm RB5 with the imx577 sensor I found that unlike on other platforms such as the Lenovo x13s/ov5675 the image was constantly getting darker and darker. At first I assumed a bug in SoftISP but, looking into the code it appeared SoftISP was requesting higher and higher exposure values which resulted in the image getting progressively darker. To my mind the software contract between user-space and kernel should be increasing exposure requests always meant higher exposure but, to be certain I asked around on IRC. Those polled agreed in principle that the software contract was consistent across sensors. 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. As a first pass I'm submitting the fix for the sensor I have but, I expect if this fix is acceptable upstream it should be pushed to most of the imx sensors with what seems to be copy/paste code for the exposure. --- Changes in v3: - Fixes non sequitur in commit log - Applies RB from Jacopo and Gjorgji - Link to v2: https://lore.kernel.org/r/20240506-b4-linux-next-camss-x13s-mmsol-integration-in-test-imx577-fix-v2-1-2e665f072f8f@linaro.org Changes in v2: - Fix typo in patch 42 -> 412 - Link to v1: https://lore.kernel.org/r/20240506-b4-linux-next-camss-x13s-mmsol-integration-in-test-imx577-fix-v1-1-4b3a9426bde8@linaro.org --- drivers/media/i2c/imx412.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) --- base-commit: ff3959189f1b97e99497183d76ab9b007bec4c88 change-id: 20240506-b4-linux-next-camss-x13s-mmsol-integration-in-test-imx577-fix-f1fee6070641 Best regards,