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SubjectRe: [linux-sunxi] [PATCH 3/7] drm/sun4i: Add SAT and DRC drivers
Hi Peter,

On Sun, Sep 04, 2016 at 10:03:06PM +0200, Peter Korsgaard wrote:
> >>>>> "Maxime" == Maxime Ripard <maxime.ripard@free-electrons.com> writes:
>
> Hi,
>
> > The A33 pipeline also has some new components called SAT and DRC. Even
> > though their exact features and programming model is not known (or
> > documented), they need to be clocked for the pipeline to carry the video
> > signal all the way.
>
> > Add minimal drivers for those that just claim the needed resources for the
> > pipeline to operate properly.
>
> > Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
> > ---
> > .../bindings/display/sunxi/sun4i-drm.txt | 37 +++++++
> > drivers/gpu/drm/sun4i/Makefile | 3 +-
> > drivers/gpu/drm/sun4i/sun6i_drc.c | 117 +++++++++++++++++++++
> > drivers/gpu/drm/sun4i/sun8i_sat.c | 105 ++++++++++++++++++
> > 4 files changed, 261 insertions(+), 1 deletion(-)
> > create mode 100644 drivers/gpu/drm/sun4i/sun6i_drc.c
> > create mode 100644 drivers/gpu/drm/sun4i/sun8i_sat.c
>
> > diff --git a/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt b/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt
> > index d467ea93ac08..87c3c8dd34cb 100644
> > --- a/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt
> > +++ b/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt
> > @@ -51,6 +51,43 @@ Required properties:
> > second the block connected to the TCON channel 1 (usually the TV
> > encoder)
>
> > +SAT
> > +---
> > +
> > +The SAT, found in the A33, allows to do some color correction.
> > +
> > +Required properties:
> > + - compatible: value must be one of:
> > + * allwinner,sun8i-a33-sat
> > + - reg: base address and size of the memory-mapped region.
> > + - clock: phandles to bus clock feeding the SAT
> > + - resets: phandles to the reset line driving the SAT
> > +
> > +- ports: A ports node with endpoint definitions as defined in
> > + Documentation/devicetree/bindings/media/video-interfaces.txt. The
> > + first port should be the input endpoints, the second one the outputs
> > +
> > +DRC
> > +---
> > +
> > +The DRC, found in the latest Allwinner SoCs (A31, A23, A33), allows to
> > +do some backlight control to enhance the power consumption.
>
> 'Enhance the power consumption'? That doesn't sound like something you
> would want ;) Presumably it is something to allow you to save power by
> dynamically adjusting LCD backlight and pixel brightness/contrast
> depending on screen content? I believe this is typically called content
> adaptive backlight control:
>
> https://www.ecnmag.com/article/2010/04/content-adaptive-lcd-backlight-control
>
> You spell out what DRC and SAT stands for in the driver source code,
> perhaps it also makes sense to do it here?
>
> Perhaps rewording it to something like this is clearer:
>
> .. allows to dynamically adjust pixel brightness/contrast based on
> histogram measurements for LCD content adaptive backlight control.

You're right, I changed it.

Thanks!
Maxime

--
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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