After any "soft gfx reset" we must manually invalidate the TLBs
associated with each ring. Empirically, it seems that a
suspend/resume or D3-D0 cycle count as a "soft reset". The symptom is
that the hardware would fail to note the new address for its status
page, and so it would continue to write the shadow registers and
breadcrumbs into the old physical address (now used by something
completely different, scary). Whereas the driver would read the new
status page and never see any progress, it would appear that the GPU
hung immediately upon resume.

Based on a patch by naresh kumar kachhi <naresh.kumar.kacchi@intel.com>
Reported-by: Thiago Macieira <thiago@kde.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=64725Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Thiago Macieira <thiago@kde.org>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>