Re: Radeon DRM GART mapping bogosity

[Vladimir D. <vo...@mi...>]

On Wed, 4 May 2005, Benjamin Herrenschmidt wrote:

>
>>> Note that with huge VRAM sizes appearing, we also want to make sure that
>>> wheverver we put it won't overlap the 32 bits space since CONFIG_MEM_SIZE
>>> can be huge nowadays... and if it does, put the GART just _before_ the
>>> framebuffer instead. Again, this is all cards space, not bus view, so that
>>> shouldn't matter where we put these things.
>>
>> Another constraint is that the GART doesn't overlap with the bus address
>> range of system RAM.
>
> Do we still care about that ? Do we ever do DMA from the card to system
> RAM outside of the AGP context ?

This is very useful for traffic from video memory to system memory - 
for example for video capture.

                      best

                         Vladimir Dergachev

>
> I think a good strategy is to try to put the AGP aperture after the
> video RAM, and if that doesn't fit, just before. That would keep us
> "high enough" in most cases to avoid system RAM, but we can't guarantee
> 100% here.
>
> Ben.
>
>
>
>
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