Am 18.08.2016 um 09:52 schrieb Michel Dänzer: > On 18/08/16 04:41 PM, Christian König wrote: >>> Afaiu the prime importing display gpu generates its own gem buffer >>> handle (prime_fd_to_handle) from that dmabuf, importing scather-gather >>> tables to access the dmabuf in system ram. As far as page flipping is >>> concerned, so far those gem buffers / radeon_bo's aren't treated any >>> different than native ones. During pageflip setup they get pinned into >>> VRAM, which moves (=copies) their content from the RAM dmabuf backing >>> store into VRAM. >> Your understanding isn't correct. Buffers imported using prime always >> stay in GTT, they can't be moved to VRAM. > That's the theory, but based on Mario's description it's clear that > there is at least one bug which either actually allows a shared buffer > to be moved to VRAM, or at least doesn't propagate the error correctly, > so the page flip operation "succeeds". > > >> It's the DDX which copies the buffer content from the imported prime >> handle into a native on which is enabled to scan out. > There is no such code which could explain what Mario is seeing.
How should this work then otherwise? I agree that I don't understand fully either what is happening here, but I find it quite unlikely that we actually scan out from system memory without the proper hardware setup. On the other hand that we accidentally move a prime imported buffer to VRAM could be possible, but this would clearly be a rather severe bug we hopefully have noticed already. Any other idea what actually happens here? Regards, Christian.
