Commits
Chris Wilson committed f2a0409a085
drm/i915/execlists: Reset RING registers upon resume commit bafb2f7d4755bf1571bd5e9a03b97f3fc4fe69ae upstream. There is a disparity in the context image saved to disk and our own bookkeeping - that is we presume the RING_HEAD and RING_TAIL match our stored ce->ring->tail value. However, as we emit WA_TAIL_DWORDS into the ring but may not tell the GPU about them, the GPU may be lagging behind our bookkeeping. Upon hibernation we do not save stolen pages, presuming that their contents are volatile. This means that although we start writing into the ring at tail, the GPU starts executing from its HEAD and there may be some garbage in between and so the GPU promptly hangs upon resume. Testcase: igt/gem_exec_suspend/basic-S4 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96526 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/20160921135108.29574-3-chris@chris-wilson.co.uk Cc: Eric Blau <eblau1@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>