Radeon DRM GART mapping bogosity

[Jerome Glisse]

On 5/3/05, Benjamin Herrenschmidt <benh at kernel.crashing.org> wrote:
> Ok, I'm cross posting here because X.org is doing it wrong too. On R300,
> for some reason I don't fully understand, it just goes back to the "old"
> way of putting the FB at 0 (though it does properly use CONFIG_MEMSIZE
> to set the size part of MC_FB_LOCATION), but for non R300, it does try
> to put the framebuffer at the same address as the BAR ... and then tries
> to use CONFIG_APER_SIZE for the size part of MC_FB_LOCATION, which is
> incorrect.
> 
> The result is that on !r300, it won't crash since X.Org and DRI won't
> create an overlapping mapping, but they won't be able to use all of VRAM
> of some cards where CONFIG_APER_SIZE < CONFIG_MEM_SIZE, and on r300, it
> will possibly create overlapping mappings and will cause all sorts of
> troubles if you get the above case.

Has i still doesn't understand the big pictures of video drivers, i
was wondering
if this could have an impact on bytes swapping on r300. Thus the problem
of bit blit we have on r300 & X driver. I don't think so but as i don't well
understand all this... 

Jerome Glisse