[libcamera-devel] [PATCH] ipa: raspberrypi: Limit minimum exposure time for the IMX296

[David Plowman]

Hi Naush

Thanks for the patch!

On Wed, 28 Sept 2022 at 08:09, Jacopo Mondi via libcamera-devel
<libcamera-devel at lists.libcamera.org> wrote:
>
> Hi Naush
>
> On Mon, Sep 26, 2022 at 10:36:39AM +0100, Naushir Patuck via libcamera-devel wrote:
> > Limit the minimum allowable exposure time to a single line in the IMX296 camera
> > helper. This equates to approximately 30us.
> >
> > Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
>
> Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>

Reviewed-by: David Plowman <david.plowman at raspberrypi.com>

Thanks!
David

>
> Thanks
>   j
>
> > ---
> >  src/ipa/raspberrypi/cam_helper_imx296.cpp | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/src/ipa/raspberrypi/cam_helper_imx296.cpp b/src/ipa/raspberrypi/cam_helper_imx296.cpp
> > index 09f828ea6249..66d21e36ecd0 100644
> > --- a/src/ipa/raspberrypi/cam_helper_imx296.cpp
> > +++ b/src/ipa/raspberrypi/cam_helper_imx296.cpp
> > @@ -26,6 +26,7 @@ public:
> >       void getDelays(int &exposureDelay, int &gainDelay, int &vblankDelay) const override;
> >
> >  private:
> > +     static constexpr uint32_t minExposureLines = 1;
> >       static constexpr uint32_t maxGainCode = 239;
> >       static constexpr Duration timePerLine = 550.0 / 37.125e6 * 1.0s;
> >
> > @@ -54,12 +55,12 @@ double CamHelperImx296::gain(uint32_t gainCode) const
> >
> >  uint32_t CamHelperImx296::exposureLines(Duration exposure) const
> >  {
> > -     return (exposure - 14.26us) / timePerLine;
> > +     return std::max<uint32_t>(minExposureLines, (exposure - 14.26us) / timePerLine);
> >  }
> >
> >  Duration CamHelperImx296::exposure(uint32_t exposureLines) const
> >  {
> > -     return exposureLines * timePerLine + 14.26us;
> > +     return std::max<uint32_t>(minExposureLines, exposureLines) * timePerLine + 14.26us;
> >  }
> >
> >  void CamHelperImx296::getDelays(int &exposureDelay, int &gainDelay,
> > --
> > 2.25.1
> >