On 01/09/2012 12:13 PM, Peter Korsgaard :
>>>>>> "Nicolas" == Nicolas Ferre <nicolas.ferre@xxxxxxxxx> writes:
>
> Nicolas> On 10/13/2011 04:52 PM, Peter Korsgaard :
> >> Allow framebuffer to be configured in 16bit mode when panel is wired in
> >> (the default) BGR configuration, and don't claim to support 15bit input
> >> modes, which the LCD controller cannot handle.
> >>
> >> Signed-off-by: Peter Korsgaard <jacmet@xxxxxxxxxx>
>
> Nicolas> Hi Peter,
>
> Nicolas> Sorry for not having more responsive concerning the two
> Nicolas> patches that you posted about atmel_lcdfb driver.
>
> No problem.
>
> Nicolas> I have a question though about this one...
>
> >> - } else if (sinfo->lcd_wiring_mode == ATMEL_LCDC_WIRING_RGB555) {
> >> - var->red.offset = 10;
> >> - var->blue.offset = 0;
> >> - var->green.length = 5;
>
> Nicolas> Maybe I have missed something but I do not know why you are removing
> Nicolas> this part of the configuration? A board at least is using this wiring
> Nicolas> mode...
>
> Because it is arguable wrong as far as I understand the HW.
> There's two parts here:
>
> - 1: Format of framebuffer memory
> - 2: Wiring of LCD (RGB/BGR order and number of bits)
>
>>From the datasheet, the following framebuffer formats are supported:
>
> 1, 2, 4, 8 bits per pixel (palletized), 16, 24 bits per pixel
> (non-palletized) for TFT.
>
> So it doesn't really support RGB555 mode. The controller reads up to
> 32bit of framebuffer data and outputs 24bit on the LCD pins. You CAN
> wire up a RGB555 panel by just skipping the LSB green of a RGB565
> wiring, but that is independent of the framebufffer format. The
> controller/driver doesn't do any RGB/BGR swapping, so the RBG/BGR wiring
> settings are just used as a software hint (in FBIOGET_VSCREENINFO) about
> the meaning of the individual bits of a pixel in the framebuffer.
>
> Similar you can connect a 12bit 4:4:4 panel by just connecting it to the
> MSB LCD pins.
Yes. Thanks to Russell and you for the explanation.
I acknowledge your two patches right now.
> So in conclusion, I think we should just have:
>
> - ATMEL_LCDC_WIRING_RGB
> - ATMEL_LCDC_WIRING_BGR
> - ATMEL_LCDC_WIRING_RGB565
> - ATMEL_LCDC_WIRING_BGR565
>
> These simply define framebuffer bit order (RGB/BGR) and preferred
> default bit depth (16/24).
Maybe we can think about a patch that removes the RGB555 variable from
the header (include/video/atmel_lcdc.h) and the board file that is using
it (board-neocore926.c).
Best regards,
--
Nicolas Ferre
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