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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. No, I don't think so. Why do you think so? I'm pretty sure that gcc is allowed to do memcpy-like tricks even when memcpy is not mentioned explicitely. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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