On Mit, 2012-04-18 at 20:20 +1000, Benjamin Herrenschmidt wrote:
> On Wed, 2012-04-18 at 10:02 +0200, Michel Dänzer wrote:
> >
> > > GPU lockup appears to be a common problem with the radeon driver.
> >
> > It's what happens when anything goes wrong with the GPU. If it doesn't
> > happen with agpmode=-1, it's probably an AGP related coherency issue.
>
> I had some success hacking the DRM to do an in_le32 from the ring head
> after writing it. Just a gross hack but it seemed to help on a G5.
AFAICT radeon_ring_commit() does that already:
DRM_MEMORYBARRIER();
WREG32(ring->wptr_reg, (ring->wptr << ring->ptr_reg_shift) &
ring->ptr_reg_mask);
(void)RREG32(ring->wptr_reg);
We added the readback about a decade ago. :)
> I suspect there's a fundamental design issue with apple bridge in that
> the CPU to memory path isn't coherent at all with the GPU to memory path
> ie. even vs. cache flush instructions (ie buffers in the memory
> controllers can still be out of sync).
>
> Darwin does some gross hacks to work around that, some of them visible
> in the AGP drivers, some burried in the Apple driver, I don't know for
> sure. It's possible that they end up mapping all AGP memory as cache
> inhibited, but we can't do that because of our linear mapping.
We are doing that though...
--
Earthling Michel Dänzer | http://www.amd.com
Libre software enthusiast | Debian, X and DRI developer
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
