[U-Boot] [PATCH] video: sunxi: Enable cache for the framebuffer

[Hans de Goede]

Hi,

On 31-01-15 02:21, Siarhei Siamashka wrote:
> Because the framebuffer resides in a hidden chopped off part of DRAM,
> caching is not enabled for this area automatically when the MMU is
> configured. So it needs to be set explicitly.
>
> Additionally, the cfb console has a function to check whether the
> framebuffer resides in DRAM or not. And the hidden sunxi framebuffer
> needs special treatment again.
>
> This fix resolves the sluggish scrolling problem.
>
> Signed-off-by: Siarhei Siamashka <siarhei.siamashka at gmail.com>

Thanks for figuring this out!

As already discussed it seems that the problem is that using
CONFIG_SYS_MEM_TOP_HIDE seems to be the wrong thing to do.

So I've written a patch with results in the same behavior in a slightly
different way, with as added bonus that we can give back unused memory
to the kernel when booting.

I'll Cc you on the patch-set when I send it.

Regards,

Hans

> ---
>   drivers/video/cfb_console.c   |  2 +-
>   drivers/video/sunxi_display.c | 10 ++++++++++
>   2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/video/cfb_console.c b/drivers/video/cfb_console.c
> index a81affa..23b50df 100644
> --- a/drivers/video/cfb_console.c
> +++ b/drivers/video/cfb_console.c
> @@ -2090,7 +2090,7 @@ static void *video_logo(void)
>   }
>   #endif
>
> -static int cfb_fb_is_in_dram(void)
> +__weak int cfb_fb_is_in_dram(void)
>   {
>   	bd_t *bd = gd->bd;
>   #if defined(CONFIG_ARM) || defined(CONFIG_AVR32) || defined(COFNIG_NDS32) || \
> diff --git a/drivers/video/sunxi_display.c b/drivers/video/sunxi_display.c
> index f5f24fc..22a1319 100644
> --- a/drivers/video/sunxi_display.c
> +++ b/drivers/video/sunxi_display.c
> @@ -1060,6 +1060,12 @@ static const char *sunxi_get_mon_desc(enum sunxi_monitor monitor)
>   	return NULL; /* never reached */
>   }
>
> +/* The framebuffer is in DRAM, even though it is in the hidden part of it */
> +int cfb_fb_is_in_dram(void)
> +{
> +	return 1;
> +}
> +
>   void *video_hw_init(void)
>   {
>   	static GraphicDevice *graphic_device = &sunxi_display.graphic_device;
> @@ -1079,6 +1085,10 @@ void *video_hw_init(void)
>   	       CONFIG_SUNXI_FB_SIZE >> 10);
>   	gd->fb_base = gd->ram_top;
>
> +	mmu_set_region_dcache_behaviour(gd->fb_base,
> +					CONFIG_SUNXI_FB_SIZE,
> +					DCACHE_WRITEBACK);
> +
>   	video_get_ctfb_res_modes(RES_MODE_1024x768, 24, &mode,
>   				 &sunxi_display.depth, &options);
>   #ifdef CONFIG_VIDEO_HDMI
>