etnaviv page faults, usually at startup
Usually at startup, sometimes the following kernel log line is printed
etnaviv-gpu 59000000.bb2d: MMU fault status 0x00000002
and things hang for a couple of seconds while it recovers.
Initial tracing suggests that shortly before, an EXA composite with negative source x-coord is sent by the X11 driver, which is almost certainly the cause. As this negative x-coord only seems to happen once at startup, the easiest solution is probably just to drop this composite. But maybe this needs to be handled as a special case, or suppressed higher up the chain.