[U-Boot] [PATCH v2 1/2] sunxi: video: Add lcd output support

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 01-01-15 21:21, Siarhei Siamashka wrote:
> On Wed, 31 Dec 2014 13:07:20 +0100
> Hans de Goede <hdegoede@redhat.com> wrote:
>
>> Add lcd output support, see the new Kconfig entries and doc/README.video for
>> how to enable / configure this.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

<snip>

>> @@ -179,7 +178,21 @@ struct sunxi_hdmi_reg {
>>   #define SUNXI_LCDC_CTRL_IO_MAP_TCON0		(0 << 0)
>>   #define SUNXI_LCDC_CTRL_IO_MAP_TCON1		(1 << 0)
>>   #define SUNXI_LCDC_CTRL_TCON_ENABLE		(1 << 31)
>> +#define SUNXI_LCDC_FRAME_CTRL0_RGB666		((1 << 31) | (0 << 4))
>> +#define SUNXI_LCDC_FRAME_CTRL0_RGB656		((1 << 31) | (5 << 4))
>
> This would be probably SUNXI_LCDC_FRAME_CTRL0_RGB565 according to
> the Allwinner documentation of the TCON0_FRM_CTL_REG register:
>
>   0: 6bit frm output
>   1: 5bit frm output
>
> Since we have 5 there (101 bit pattern), it simply means RGB565.

You're completely right, I took over the weird RGB656 naming from the
allwinner kernel code without thinking things through properly.


<snip>

>> +	bp = mode->vsync_len + mode->upper_margin;
>> +	total = mode->yres + mode->lower_margin + bp;
>> +	writel(SUNXI_LCDC_TCON0_TIMING_V_TOTAL(total) |
>> +	       SUNXI_LCDC_TCON0_TIMING_V_BP(bp), &lcdc->tcon0_timing_v);
>> +
>> +	writel(SUNXI_LCDC_X(mode->hsync_len) | SUNXI_LCDC_Y(mode->vsync_len),
>> +	       &lcdc->tcon0_timing_sync);
>> +
>> +	/* We only support hv-sync parallel lcd-s for now */
>> +	writel(0, &lcdc->tcon0_hv_intf);
>> +	writel(0, &lcdc->tcon0_cpu_intf);
>> +
>> +	if (sunxi_display.depth == 18 || sunxi_display.depth == 17) {
>
> Here 17 is not quite correct for RGB565.

Right, this should be 16 meaning plain old RGB565, I've fixed both in
my personal tree. Thanks for pointing this out!



>
> Also these are dithering settings, and this code just unconditionally
> enables the right dithering for 16-bit LCD displays (this seems to
> be never used in any real device from the sunxi-boards repository) or
> 18-bit LCD displays, which are very common.
>
> Because 32-bit framebuffers support more colors than the 18-bit LCD
> hardware can show, dithering is needed and used:
>      http://en.wikipedia.org/wiki/Frame_rate_control
>
> Do we want to have a separate option to enable/disable dithering? Or
> just keep it always enabled until somebody complains?
>
> A simple program for testing dithering effects/usefulness can be found
> here:
>      http://lists.denx.de/pipermail/u-boot/2015-January/200031.html

<snip>

Regards,

Hans