[PATCH 00/26] x86: video: Speed up the framebuffer

Simon Glass
2020-05-22T16:33:48Z

Hi Bin,

On Fri, 22 May 2020 at 09:30, Bin Meng <bmeng.cn@gmail.com> wrote:
>
> Hi Simon,
>
> On Wed, May 20, 2020 at 7:11 AM Simon Glass <sjg@chromium.org> wrote:
> >
> > Some architectures use a cached framebuffer and flush the cache as needed
> > so that changes are visible. This is supported by U-Boot.
> >
> > However x86 uses an uncached framebuffer with a 'write-combining' feature
> > to speed up writes. Reads are permitted but they are extremely expensive.
> >
>
> Is it possible to use cached framebuffer on x86?

It might be possible on newer chips. I see so much conflicting stuff
about flushing the cache, though. The write-through cache is slow for
reads. The write-back cache never writes unless you flush.

>
> > Unfortunately, reading from the frame buffer is quite common, e.g. to
> > scroll it. This makes scrolling very slow.
> >
> > This series adds a new feature which supports copying modified parts of
> > the frame buffer to the uncached hardware buffer. This speeds up scrolling
> > dramatically on x86 so the extra complexity cost seems worth it.
> >
> > In an extreme case, the time to print the environment on minnowboard with
> > 1280x1024 and CONFIG_CONSOLE_SCROLL_LINES disabled is reduced
> > significantly, from 13 seconds to 300ms.
> >
>
> Thanks for the series. The improvements sounds great! I will get one
> minnowmax board to test this series soon.

Yes it should work on that.

Regards,
Simon