RG280M (and possibly other devices) panel driver settings

[citral23]

This panel has its subpixels in delta arrangement fed by a serial bus. A built-in filter can be used to make it perform as a standard RGB device (PIXELCOLORWIRE)

The formula to find the right timings and get a perfect 60Hz is (320+(x/3))*(480+y)3Hz=PixelClock. Thus we can use htotal=485, vtotal=640 and a pixel clock of 43,2MHz to get a perfect 60Hz refresh.

It presents a challenge, as if everything is set up as it should in theory, the last blue subpixel vertical line does not light up on the right side of the screen.

A workaround is to send GBR (via a reg_map in the ingenic drm driver) and offset HPOSITION by -1, that covers the last subpixel but that code will need to be conditioned, which pcercuei said he will do.

Signed-off-by: Christophe Branchereau cbranchereau@gmail.com

[pcercuei]

This is actually not correct. From these timings, the DRM core will compute that you have a 43,2 MHz / ((320+100+30+35)*(480+124+20+16)) == 139,18 Hz panel. The fact that you do get a 60.0 Hz image from these timings is because the ingenic-drm driver doesn't compute the right hardware values in the case where a serial 8bpp panel is used. Hence the "x3" added there (but this might be wrong).

[citral23]

Here are timings/hposition that work keeping the "x3"s in the ingenic drm driver (keeping the reg_map(priv->map, 0x90, 0x33) ; )

{ 0x04, REG04_HPOSITION1(0xd1) }

static const struct drm_display_mode y030xx067a_modes[] = {
{
.clock = 54000,
.hdisplay = 320,
.hsync_start = 320 + 90,
.hsync_end = 320 + 90 + 37,
.htotal = 320 + 90 + 37 + 33,
.vdisplay = 480,
.vsync_start = 480 + 109,
.vsync_end = 480 + 109 + 20,
.vtotal = 480 + 109 + 20 + 16,
.flags = DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC,
},
};

480x625x60x3=54M

[pcercuei]

RG280M support is now available in the latest jz-5.9 branch thanks to @citral23. Closing this PR now.