UBUNTU: SAUCE: drm/i915/gen8+: Add RC6 CTX corruption WA

UBUNTU: SAUCE: drm/i915/gen8+: Add RC6 CTX corruption WA

In some circumstances the RC6 context can get corrupted. We can detect
this and take the required action, that is disable RC6 and runtime PM.
The HW recovers from the corrupted state after a system suspend/resume
cycle, so detect the recovery and re-enable RC6 and runtime PM.

v2: rebase (Mika)
v3:
- Move intel_suspend_gt_powersave() to the end of the GEM suspend
  sequence.
- Add commit message.
v4:
- Rebased on intel_uncore_forcewake_put(i915->uncore, ...) API
  change.
v5: rebased on gem/gt split (Mika)

Signed-off-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
CVE-2019-0154

[tyhicks: Backport to 4.15
 - Don't use intel_wakeref_t since it doesn't exist. I followed Intel's
   lead by copying what they did in their 4.19-stable backport.
 - Take dev_priv->pcu_lock in intel_disable_rc6(). I followed Intel's
   lead by copying what they did in their 4.19-stable backport.
 - Use INTEL_GEN() instead of IS_GEN()
 - Quite a few context adjustments throughout the entire patch]
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>