[U-Boot] [PATCH 3/3] sunxi: display: Add overscan correction
Ian Campbell
ijc+uboot at hellion.org.uk
Wed Aug 12 12:45:40 CEST 2015
On Wed, 2015-08-05 at 17:17 +0200, Hans de Goede wrote:
> > > sunxi_display.fb_size =
> > > > (mode->xres * mode->yres * 4 + 0xfff) & ~0xfff;
> +> > overscan_offset = (overscan_y * mode->xres + overscan_x) * 4;
> +> > /* We want to keep the fb_base for simplefb page aligned, where as
> +> > * the sunxi dma engines will happily accept an unaligned address. */
> +> > if (overscan_offset)
> +> > > sunxi_display.fb_size += 0x1000;
Why plus 4K regardless of the magnitude of overscan_offset? What if it was
0x1004?
Also, what's the link between fb_base's alignment and fb_size which is
implied by the comment?
> > > gd->fb_base = gd->bd->bi_dram[0].start +
> > > > gd->bd->bi_dram[0].size - sunxi_display.fb_size;
> > > sunxi_engines_init();
> -> > sunxi_mode_set(mode, gd->fb_base - CONFIG_SYS_SDRAM_BASE);
> +
> +> > fb_dma_addr = gd->fb_base - CONFIG_SYS_SDRAM_BASE;
> +> > sunxi_display.fb_addr = gd->fb_base;
> +> > if (overscan_offset) {
> +> > > fb_dma_addr += 0x1000 - (overscan_offset & 0xfff);
> +> > > sunxi_display.fb_addr += (overscan_offset + 0xfff) & ~0xfff;
> +> > > memset((void *)gd->fb_base, 0, sunxi_display.fb_size);
> +> > > flush_cache(gd->fb_base, sunxi_display.fb_size);
> +> > }
Hrm, I think this starts to answer, but I'm still not sure I follow, sorry.
> + sunxi_mode_set(mode, fb_dma_addr);
>
> /*
> > > * These are the only members of this structure that are used. All the
> > > * others are driver specific. There is nothing to decribe pitch or
Pre-existing typo "describe".
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