On Thu, Aug 2, 2018 at 12:31 PM Mikulas Patocka <mpato...@redhat.com> wrote: > > Hi > > I tried to use a PCIe graphics card on the MacchiatoBIN board and I hit a > strange problem. > > When I use the links browser in graphics mode on the framebuffer, I get > occasional pixel corruption. Links does memcpy, memset and 4-byte writes > on the framebuffer - nothing else. > > I found out that the pixel corruption is caused by overlapping unaligned > stp instructions inside memcpy. In order to avoid branching, the arm64 > memcpy implementation may write the same destination twice with different > alignment. If I put "dmb sy" between the overlapping stp instructions, the > pixel corruption goes away. > > This seems like a hardware bug. Is it a known errata? Do you have any > workarounds for it?
Yes fix Links not to use memcpy on the framebuffer. It is undefined behavior to use device memory with memcpy. Thanks, Andrew Pinski > > I tried AMD card (HD 6350) and NVidia (NVS 285) and both exhibit the same > corruption. OpenGL doesn't work (it results in artifacts on the AMD card > and lock-up on the NVidia card), but it's quite expected if even simple > writing to the framebuffer doesn't work. > > Mikulas
