drm/i915/tgl: Disable rc6 for debugging

Empirical evidence from CI tells us that our rc6 setup for Tigerlake is
off. Disable rc6 on tgl temporary so that we gain CI coverage as we
prepare a fix. It also appears that the BIOS on our tgl leaves rc6
enabled, so we have to explicitly disable it on init.

References: https://bugs.freedesktop.org/show_bug.cgi?id=111593Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Acked-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190910161657.23037-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_pci.c

@@ -797,6 +797,7 @@ static const struct intel_device_info intel_tigerlake_12_info = {
 	.display.has_modular_fia = 1,
 	.engine_mask =
 		BIT(RCS0) | BIT(BCS0) | BIT(VECS0) | BIT(VCS0) | BIT(VCS2),
+	.has_rc6 = false, /* XXX disabled for debugging */
 };
 
 #undef GEN

drivers/gpu/drm/i915/intel_pm.c

@@ -8671,8 +8671,7 @@ void intel_disable_gt_powersave(struct drm_i915_private *dev_priv)
 {
 	mutex_lock(&dev_priv->gt_pm.rps.lock);
 
-	if (HAS_RC6(dev_priv))
-		intel_disable_rc6(dev_priv);
+	intel_disable_rc6(dev_priv);
 
 	intel_disable_rps(dev_priv);
 	if (HAS_LLC(dev_priv))