When we blit data into a buffer object, we may need to invalidate any
caches that might contain stale data, so the new data becomes visible.
For example, if the buffer object is bound as a vertex buffer, we need
to invalidate the vertex fetch cache.
While this flushing was missing, it usually happened implicitly for
non-obvious reasons: we're usually on the render ring, and calling
intel_emit_linear_blit() would require switching to the BLT ring,
causing an implicit flush. This likely provoked the kernel to do
PIPE_CONTROLs on our behalf. Although, Gen4-5 wouldn't have this
behavior. At any rate, we should do it ourselves.
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Kenneth Graunke
3efedf98e8