On Thu, Apr 19, 2018 at 3:02 PM, Chen-Yu Tsai <wens@xxxxxxxx> wrote: > Dithering is a method of approximating a color from a mixture of other > colors when the required color isn't available. It reduces color > banding artifacts that can be observed when displaying gradients > (e.g. grayscale gradients). This may occur when the image that needs > to be displayed is 24-bit but the LCD panel is a lower bit depth and > does not perform dithering on its own. > > The TCON (LCD controller) found in Allwinner SoCs has hardware support > for dithering on channel 0, the channel used to feed LCD panels. This > series adds support for it. > > Patch 1 reworks the mode set function for the CPU interface to pass > the encoder object, so it can be passed to other helper functions. > > Patch 2 renames the dithering related register macros to reflect the > fact that dithering is only supported on channel 0. > > Patch 3 adds support for dithering on all LCD panel output types. > > Patch 4 adds support for Banana Pi's 7" DPI LCD panel. > > Patch 5 adds a pinmux setting for RGB888 for the Allwinner A20 SoC. > This change has been sent by others before. > > Patch 6 provides an example for enabling the Banana Pi 7" DPI LCD panel > on the Banana Pi M1+. This should not be merged. I will likely rework > this into an overlay in the future. > > Note that I was only able to test dithering with DPI, as I do not have > other panel types. However the underlying concept and core code is the > same, as are the drm objects accessed. Nevertheless I'm hoping Jonathan > can test LVDS and Maxime can test MIPI DSI. > > Also it seems pwm-backlight hardware is unusable at the moment. I'm not > sure whether the pwm-backlight or sun4i-pwm driver is to blame. I had to > manually poke the pwm registers so the LCD backlight wouldn't be > completely black. > > > Regards > ChenYu > > Chen-Yu Tsai (5): > drm/sun4i: tcon: Pass drm_encoder * into sun4i_tcon0_mode_set_cpu > drm/sun4i: tcon: Rename Dithering related register macros > drm/panel: simple: Add support for Banana Pi 7" S070WV20-CT16 panel > ARM: dts: sun7i: add pinmux setting for RGB888 output for LCD0 > [DO NOT MERGE] ARM: dts: sun7i: bananapi-m1-plus: Enable Bananapi 7" > 800x480 RGB LCD panel > > Jonathan Liu (1): > drm/sun4i: tcon: Add dithering support for RGB565/RGB666 LCD panels Do you have any working branch to test this, I can't see drm probing on linux-next, I even enabled de on dts which is missing. Jagan.
