[U-Boot] [PATCH 3/4] tegra: video: Always use write-through cache on LCD

[Simon Glass]

Hi Thierry,

On 20 January 2016 at 07:53, Thierry Reding <thierry.reding at gmail.com> wrote:
> On Mon, Jan 18, 2016 at 01:07:10PM -0700, Stephen Warren wrote:
>> On 01/14/2016 01:26 PM, Simon Glass wrote:
>> >This seems to give the best performance, so let's use it always.
>>
>> I thought we chose the current cache mode due to display corruption issues
>> with other modes, but I tested a change that I believe does the same as this
>> change on Seaboard without any apparent issue so,
>>
>> Acked-by: Stephen Warren <swarren at nvidia.com>
>
> I think for framebuffers the best option is still write-combine, which
> would be something like:
>
>         DCACHE_WRITECOMBINE = DCACHE_OFF | TTB_SECT_B_MASK
>
> on ARM v7. Did you ever benchmark that against DCACHE_WRITETHROUGH? It
> should be faster provided that you never read from the region.

This is noticeably slower in my experience. Reading from the region is
pretty common - e.g. scrolling.

Regards,
Simon