[libcamera-devel] [PATCH] ipa: ipu3: af: Set default grid block width to the minimum value

[Kate Hsuan]

Hi Jean-Michel,

On Tue, Mar 22, 2022 at 2:17 PM Jean-Michel Hautbois
<jeanmichel.hautbois at ideasonboard.com> wrote:
>
> Hi Kate,
>
> On 22/03/2022 02:31, Kate Hsuan via libcamera-devel wrote:
> > Since x       coordinate is incorrectly computed by a kernel issue, the block width
> > should be set to 4 to prevent using the second stripe when setting the AF scene
> > to the centre of the image. A kernel patch had fixed this issue. Therefore, this
> > value can be set to the default minimum value.
>
> If this is working fine with a width of 256 (2**4 * 16), why do you want
> to change it to have a smaller focus region ?
>
> >
> > Signed-off-by: Kate Hsuan <hpa at redhat.com>
> > ---
> > The kernel patch is shown as following URL.
> > https://lore.kernel.org/linux-media/CAEth8oES8abPO4p7eFv43PwDXuxeOmg1661YtVvykBPrkagzKg@mail.gmail.com/T/#mb02fa73ce9e3089a4619c318badb2047a3ac39e2
> > ---
> >   src/ipa/ipu3/algorithms/af.h | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/src/ipa/ipu3/algorithms/af.h b/src/ipa/ipu3/algorithms/af.h
> > index 13c7e0e8..108fcd18 100644
> > --- a/src/ipa/ipu3/algorithms/af.h
> > +++ b/src/ipa/ipu3/algorithms/af.h
> > @@ -20,7 +20,7 @@ static constexpr uint8_t kAfMinGridWidth = 16;
> >   static constexpr uint8_t kAfMinGridHeight = 16;
> >   static constexpr uint8_t kAfMaxGridWidth = 32;
> >   static constexpr uint8_t kAfMaxGridHeight = 24;
> > -static constexpr uint16_t kAfMinGridBlockWidth = 4;
> > +static constexpr uint16_t kAfMinGridBlockWidth = 3;
> >   static constexpr uint16_t kAfMinGridBlockHeight = 3;
> >   static constexpr uint16_t kAfMaxGridBlockWidth = 6;
> >   static constexpr uint16_t kAfMaxGridBlockHeight = 6;
>

The kernel patch fixed the issue on the second (rightmost) stripe configuration.
This means we can set x_start more than 640.
Also, according to the chomiumOS implementation, it set
kAfMinGridBlockWidth to 3. So, it may align with chromium OS
implementation after the patch is merged to kernel release.
https://chromium.googlesource.com/chromiumos/platform/arc-camera/+/refs/heads/master/hal/intel/include/ia_imaging/af_public.h#36

--
BR,
Kate