KMS and TTM questions

[Alex Deucher]

On Tue, Oct 4, 2011 at 9:42 AM, James Simmons <jsimmons at infradead.org> wrote:
>
>> > Thats fine as long as you don't want to do acceleration or object
>> > migration between GTT
>> > and VRAM type memory. Now I expect when you give out this advice you
>>
>> Yes but the VIA doesn't if I recall correctly have any 'VRAM type memory'.
>> It's all effectively in the GART with the 'stolen' pages preloaded into
>> the translation tables by the BIOS at vga init time.
>>
>> It has fake VRAM type memory but thats really an illusion (although one
>> the driver seems to like to keep up). The GEM changes do mean you can
>> plug the existing allocator in the VIA driver into GEM directly. Whether
>> that would be a good idea or not given the other things you then need to
>> do I don't know - but it does seem to be me to be a stepping stone in the
>> right direction that is much easier to make ?
>
> That is correct. In fact the via driver detects what type of system ram is
> used so I can limit what resolutions are supported. Its possible that the
> memory doesn't have the bandwidth to support a very large resolution on
> older systems.

Is vram actually handled via a scatter/gather page table or is it just
a pointer to a contiguous chunk of stolen system memory at the top of
ram?

Alex