Hi Dave,
On Thu, Nov 24, 2022 at 03:10:02PM +0000, Dave Stevenson wrote:
> On Wed, 23 Nov 2022 at 11:00, Laurent Pinchart wrote:
> > On Wed, Nov 23, 2022 at 10:08:19AM +0000, Dave Stevenson wrote:
> > > On Tue, 22 Nov 2022 at 22:34, Laurent Pinchart wrote:
> > > >
> > > > The black level programmed in the BLKLEVEL register depends on the
> > > > output format. The black level value computation is currently performed
> > > > in imx290_set_ctrl(), in addition to having different black level values
> > > > in the output-specific register value tables. Move it to a separate
> > > > function to simplify the imx290_set_ctrl() code.
> > >
> > > Does this actually help?
> > > The sensor only supports 10 and 12 bpp readout, so making it generic
> > > for any bpp is rather redundant.
> > > If you are looking at having different on-sensor black level values
> > > kicking around, then tuning data goes out the window.
> >
> > This may be needed for some use cases, but that's not what I'm after
> > here. By the way, could you explain why we can't just set it to 0 in the
> > sensor and avoid subtracting it in the ISP (at least for the data
> > pedestal value that is added on purpose in the sensor, there can also be
> > an additional black level due to other reasons) ? I'm sure there's a
> > reason :-)
>
> A quick play does imply that it works with 0 being defined in both
> places, but personally I'd prefer following the manufacturer's
> guidance on this sort of setting. David P may have some bright ideas
> as to why a pedestal is desired.
>
> There is a little bit of me thinking that if it were 0, then the mono
> variant of the sensor with a lens exhibiting minimal vignetting could
> be used directly for 10 or 12bit data under controlled lighting.
> However that is a very specific and unusual use case, so not worth
> potentially compromising IQ for normal use cases.
One reason I can think of is to get the dark areas away from
non-linearities in the analogue path, but I lack visibility (no pun
intended) on the real issues this could cause. Some insight from David
would indeed be very appreciated.
> > > OK we do appear to have duplication between imx290_[10|12]bit_settings
> > > and imx290_set_ctrl, but I don't get the need to compute it.
> >
> > The idea was to centralize black level setting in a single place, to
> > prepare for the removal of he imx290->bpp field. It's really in
> > imx290_set_ctrl() that it matters, I could keep the value in the
> > imx290_10bit_settings and imx290_12bit_settings arrays, but I thought I
> > could as well do it the same way everywhere.
>
> I'd missed that it was reprogramming the black level for the test patterns.
>
> Changing the black level when choosing a test pattern seems a very odd
> thing to do. You're wanting to test the pipeline as configured for the
> sensor, but you're artificially changing the incoming data and
> therefore any processing steps are misconfigured.
Now that you mention it, it's indeed very clear that there's a problem
there. We shouldn't have to change ISP parameters when switching to a
test pattern (some things may need to change in the algorithms though,
AGC and AWB won't necessarily work nicely).
> Looking at the data it's weird. Viewing the data as
> V4L2_PIX_FMT_SRGGB12 Pattern 4 as is gives a 12 pixel pattern of
> (bytes reversed):
> 0105 0105 c204 c204 3e01 3e01 0000 0000 0000 0000 0000 0105
> repeated multiple times along each line, and then that line repeated
> vertically. So we definitely have pixels below the black level.
> Alter the black level back to the default 0xf0 and you get:
> f105 f105 b205 b205 2e02 2e02 0000 0000 9c00 9c00 0000 f105
> So it's added the offset of 0xf0 to the non-zero pixels, but only some
> of the zero ones and then not by the configured amount.
What the... :-S
> My datasheets have no reference to a PGCTRL register or 0x308c, so I
> can't say if Sony has provided any guidance on needing to change black level.
> Perhaps Manivannan has some further information on this as he added
> the test pattern support.
I thought I saw documentation about that, but it was for the IMX296, not
the IMX290.
> As it stands the code retains the existing (weird) behaviour, and
> drops the duplication, so I'll add:
>
> Reviewed-by: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx>
Thanks. We can fix the test pattern on top.
> > > > Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > > > ---
> > > > drivers/media/i2c/imx290.c | 53 +++++++++++++++++++++-----------------
> > > > 1 file changed, 29 insertions(+), 24 deletions(-)
> > > >
> > > > diff --git a/drivers/media/i2c/imx290.c b/drivers/media/i2c/imx290.c
> > > > index 135ed55592a1..d9fc6c44b0f0 100644
> > > > --- a/drivers/media/i2c/imx290.c
> > > > +++ b/drivers/media/i2c/imx290.c
> > > > @@ -152,6 +152,9 @@
> > > > #define IMX290_PIXEL_ARRAY_RECORDING_WIDTH 1920
> > > > #define IMX290_PIXEL_ARRAY_RECORDING_HEIGHT 1080
> > > >
> > > > +/* Equivalent value for 16bpp */
> > > > +#define IMX290_BLACK_LEVEL_DEFAULT 3840
> > > > +
> > > > #define IMX290_NUM_SUPPLIES 3
> > > >
> > > > struct imx290_regval {
> > > > @@ -315,7 +318,6 @@ static const struct imx290_regval imx290_10bit_settings[] = {
> > > > { IMX290_ADBIT2, IMX290_ADBIT2_10BIT },
> > > > { IMX290_ADBIT3, IMX290_ADBIT3_10BIT },
> > > > { IMX290_CSI_DT_FMT, IMX290_CSI_DT_FMT_RAW10 },
> > > > - { IMX290_BLKLEVEL, 60 },
> > > > };
> > > >
> > > > static const struct imx290_regval imx290_12bit_settings[] = {
> > > > @@ -325,7 +327,6 @@ static const struct imx290_regval imx290_12bit_settings[] = {
> > > > { IMX290_ADBIT2, IMX290_ADBIT2_12BIT },
> > > > { IMX290_ADBIT3, IMX290_ADBIT3_12BIT },
> > > > { IMX290_CSI_DT_FMT, IMX290_CSI_DT_FMT_RAW12 },
> > > > - { IMX290_BLKLEVEL, 240 },
> > > > };
> > > >
> > > > /* supported link frequencies */
> > > > @@ -516,35 +517,43 @@ static int imx290_set_data_lanes(struct imx290 *imx290)
> > > > return ret;
> > > > }
> > > >
> > > > +static int imx290_set_black_level(struct imx290 *imx290,
> > > > + unsigned int black_level, int *err)
> > > > +{
> > > > + return imx290_write(imx290, IMX290_BLKLEVEL,
> > > > + black_level >> (16 - imx290->bpp), err);
> > > > +}
> > > > +
> > > > static int imx290_write_current_format(struct imx290 *imx290)
> > > > {
> > > > + const struct imx290_regval *regs;
> > > > + unsigned int num_regs;
> > > > + unsigned int bpp;
> > > > int ret;
> > > >
> > > > switch (imx290->current_format.code) {
> > > > case MEDIA_BUS_FMT_SRGGB10_1X10:
> > > > - ret = imx290_set_register_array(imx290, imx290_10bit_settings,
> > > > - ARRAY_SIZE(
> > > > - imx290_10bit_settings));
> > > > - if (ret < 0) {
> > > > - dev_err(imx290->dev, "Could not set format registers\n");
> > > > - return ret;
> > > > - }
> > > > + regs = imx290_10bit_settings;
> > > > + num_regs = ARRAY_SIZE(imx290_10bit_settings);
> > > > + bpp = 10;
> > > > break;
> > > > case MEDIA_BUS_FMT_SRGGB12_1X12:
> > > > - ret = imx290_set_register_array(imx290, imx290_12bit_settings,
> > > > - ARRAY_SIZE(
> > > > - imx290_12bit_settings));
> > > > - if (ret < 0) {
> > > > - dev_err(imx290->dev, "Could not set format registers\n");
> > > > - return ret;
> > > > - }
> > > > + regs = imx290_12bit_settings;
> > > > + num_regs = ARRAY_SIZE(imx290_12bit_settings);
> > > > + bpp = 12;
> > > > break;
> > > > default:
> > > > dev_err(imx290->dev, "Unknown pixel format\n");
> > > > return -EINVAL;
> > > > }
> > > >
> > > > - return 0;
> > > > + ret = imx290_set_register_array(imx290, regs, num_regs);
> > > > + if (ret < 0) {
> > > > + dev_err(imx290->dev, "Could not set format registers\n");
> > > > + return ret;
> > > > + }
> > > > +
> > > > + return imx290_set_black_level(imx290, IMX290_BLACK_LEVEL_DEFAULT, &ret);
> > > > }
> > > >
> > > > /* ----------------------------------------------------------------------------
> > > > @@ -573,7 +582,7 @@ static int imx290_set_ctrl(struct v4l2_ctrl *ctrl)
> > > >
> > > > case V4L2_CID_TEST_PATTERN:
> > > > if (ctrl->val) {
> > > > - imx290_write(imx290, IMX290_BLKLEVEL, 0, &ret);
> > > > + imx290_set_black_level(imx290, 0, &ret);
> > > > usleep_range(10000, 11000);
> > > > imx290_write(imx290, IMX290_PGCTRL,
> > > > (u8)(IMX290_PGCTRL_REGEN |
> > > > @@ -582,12 +591,8 @@ static int imx290_set_ctrl(struct v4l2_ctrl *ctrl)
> > > > } else {
> > > > imx290_write(imx290, IMX290_PGCTRL, 0x00, &ret);
> > > > usleep_range(10000, 11000);
> > > > - if (imx290->bpp == 10)
> > > > - imx290_write(imx290, IMX290_BLKLEVEL, 0x3c,
> > > > - &ret);
> > > > - else /* 12 bits per pixel */
> > > > - imx290_write(imx290, IMX290_BLKLEVEL, 0xf0,
> > > > - &ret);
> > > > + imx290_set_black_level(imx290, IMX290_BLACK_LEVEL_DEFAULT,
> > > > + &ret);
> > > > }
> > > > break;
> > > > default:
--
Regards,
Laurent Pinchart
