[PATCH v2] libcamera: libipa: camera_sensor: Add onsemi AR0144 sensor properties

[Kieran Bingham]

Quoting Laurent Pinchart (2024-07-04 00:11:36)
> Provide the onsemi AR0144 camera sensor properties and registration with
> libipa for the gain code helpers.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
> Now that the kernel driver has been posted to the linux-media mailing
> list ([1]), it's time for a second version of this patch.
> 
> [1] https://lore.kernel.org/r/20240603230301.26550-1-laurent.pinchart@ideasonboard.com
> 
> Changes since RFC:
> 
> - Add default case
> - Add black level
> ---
>  src/ipa/libipa/camera_sensor_helper.cpp       | 94 +++++++++++++++++++
>  .../sensor/camera_sensor_properties.cpp       |  9 ++
>  2 files changed, 103 insertions(+)

I think I'll be able to test this soon. Might as well be in by then ;-)

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

> 
> diff --git a/src/ipa/libipa/camera_sensor_helper.cpp b/src/ipa/libipa/camera_sensor_helper.cpp
> index a1339c83c4cb..1cae0b3840af 100644
> --- a/src/ipa/libipa/camera_sensor_helper.cpp
> +++ b/src/ipa/libipa/camera_sensor_helper.cpp
> @@ -8,6 +8,7 @@
>  #include "camera_sensor_helper.h"
>  
>  #include <cmath>
> +#include <limits>
>  
>  #include <libcamera/base/log.h>
>  
> @@ -398,6 +399,99 @@ static constexpr double expGainDb(double step)
>         return log2_10 * step / 20;
>  }
>  
> +class CameraSensorHelperAr0144 : public CameraSensorHelper
> +{
> +public:
> +       CameraSensorHelperAr0144()
> +       {
> +               /* Power-on default value: 168 at 12bits. */
> +               blackLevel_ = 2688;
> +       }
> +
> +       uint32_t gainCode(double gain) const override
> +       {
> +               /* The recommended minimum gain is 1.6842 to avoid artifacts. */
> +               gain = std::clamp(gain, 1.0 / (1.0 - 13.0 / 32.0), 18.45);
> +
> +               /*
> +                * The analogue gain is made of a coarse exponential gain in
> +                * the range [2^0, 2^4] and a fine inversely linear gain in the
> +                * range [1.0, 2.0[. There is an additional fixed 1.153125
> +                * multiplier when the coarse gain reaches 2^2.
> +                */
> +
> +               if (gain > 4.0)
> +                       gain /= 1.153125;
> +
> +               unsigned int coarse = std::log2(gain);
> +               unsigned int fine = (1 - (1 << coarse) / gain) * 32;
> +
> +               /* The fine gain rounding depends on the coarse gain. */
> +               if (coarse == 1 || coarse == 3)
> +                       fine &= ~1;
> +               else if (coarse == 4)
> +                       fine &= ~3;
> +
> +               return (coarse << 4) | (fine & 0xf);
> +       }
> +
> +       double gain(uint32_t gainCode) const override
> +       {
> +               unsigned int coarse = gainCode >> 4;
> +               unsigned int fine = gainCode & 0xf;
> +               unsigned int d1;
> +               double d2, m;
> +
> +               switch (coarse) {
> +               default:
> +               case 0:
> +                       d1 = 1;
> +                       d2 = 32.0;
> +                       m = 1.0;
> +                       break;
> +               case 1:
> +                       d1 = 2;
> +                       d2 = 16.0;
> +                       m = 1.0;
> +                       break;
> +               case 2:
> +                       d1 = 1;
> +                       d2 = 32.0;
> +                       m = 1.153125;
> +                       break;
> +               case 3:
> +                       d1 = 2;
> +                       d2 = 16.0;
> +                       m = 1.153125;
> +                       break;
> +               case 4:
> +                       d1 = 4;
> +                       d2 = 8.0;
> +                       m = 1.153125;
> +                       break;
> +               }
> +
> +               /*
> +                * With infinite precision, the calculated gain would be exact,
> +                * and the reverse conversion with gainCode() would produce the
> +                * same gain code. In the real world, rounding errors may cause
> +                * the calculated gain to be lower by an amount negligible for
> +                * all purposes, except for the reverse conversion. Converting
> +                * the gain to a gain code could then return the quantized value
> +                * just lower than the original gain code. To avoid this, tests
> +                * showed that adding the machine epsilon to the multiplier m is
> +                * sufficient.
> +                */
> +               m += std::numeric_limits<decltype(m)>::epsilon();
> +
> +               return m * (1 << coarse) / (1.0 - (fine / d1) / d2);
> +       }
> +
> +private:
> +       static constexpr double kStep_ = 16;
> +};
> +REGISTER_CAMERA_SENSOR_HELPER("ar0144", CameraSensorHelperAr0144)
> +
>  class CameraSensorHelperAr0521 : public CameraSensorHelper
>  {
>  public:
> diff --git a/src/libcamera/sensor/camera_sensor_properties.cpp b/src/libcamera/sensor/camera_sensor_properties.cpp
> index b18524d85b37..4e5217ab51ef 100644
> --- a/src/libcamera/sensor/camera_sensor_properties.cpp
> +++ b/src/libcamera/sensor/camera_sensor_properties.cpp
> @@ -52,6 +52,15 @@ LOG_DEFINE_CATEGORY(CameraSensorProperties)
>  const CameraSensorProperties *CameraSensorProperties::get(const std::string &sensor)
>  {
>         static const std::map<std::string, const CameraSensorProperties> sensorProps = {
> +               { "ar0144", {
> +                       .unitCellSize = { 3000, 3000 },
> +                       .testPatternModes = {
> +                               { controls::draft::TestPatternModeOff, 0 },
> +                               { controls::draft::TestPatternModeSolidColor, 1 },
> +                               { controls::draft::TestPatternModeColorBars, 2 },
> +                               { controls::draft::TestPatternModeColorBarsFadeToGray, 3 },
> +                       },
> +               } },
>                 { "ar0521", {
>                         .unitCellSize = { 2200, 2200 },
>                         .testPatternModes = {
> 
> base-commit: 196abb8d1d6e0fe9d190315e72a85eb12d16a554
> -- 
> Regards,
> 
> Laurent Pinchart
>