Daniel Vetter <daniel@xxxxxxxx> writes: > On Fri, May 31, 2019 at 08:46:58AM -0700, Eric Anholt wrote: >> Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> writes: >> >> > Right now, the BO is mapped as a cached region when ->vmap() is called >> > and the underlying object is not a dmabuf. >> > Doing that makes cache management a bit more complicated (you'd need >> > to call dma_map/unmap_sg() on the ->sgt field everytime the BO is about >> > to be passed to the GPU/CPU), so let's map the BO with writecombine >> > attributes instead (as done in most drivers). >> > >> > Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> >> > --- >> > Found this issue while working on panfrost perfcnt where the GPU dumps >> > perf counter values in memory and the CPU reads them back in >> > kernel-space. This patch seems to solve the unpredictable behavior I >> > had. >> > >> > I can also go for the other option (call dma_map/unmap/_sg() when >> > needed) if you think that's more appropriate. >> >> writecombined was the intent, and this makes kernel vmap match the >> userspace mmap path. > > Since I missed that obviously: Where do the shmem helpers set write > combined mode for userspace mmap? That was the trick when I asked the question, too. drm_gem.c is what sets WC by default.
Attachment:
signature.asc
Description: PGP signature
_______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
