drm/i915: Never fully mask the the EI up rps interrupt on SNB/IVB

BugLink: http://bugs.launchpad.net/bugs/1615620

commit a7b4667a upstream.

SNB (and IVB too I suppose) starts to misbehave if the GPU gets stuck
in an infinite batch buffer loop. The GPU apparently hogs something
critical and CPUs start to lose interrupts and whatnot. We can keep
the system limping along by unmasking some interrupts in
GEN6_PMINTRMSK. The EI up interrupt has been previously chosen for
that task, so let's never mask it.

v2: s/gen6_rps_pm_mask/gen6_sanitize_rps_pm_mask/ (Chris)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93122Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1464014568-4529-1-git-send-email-ville.syrjala@linux.intel.com
(cherry picked from commit 12c100bf)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/gpu/drm/i915/intel_pm.c

@@ -4526,7 +4526,8 @@ void gen6_rps_idle(struct drm_i915_private *dev_priv)
 		else
 			gen6_set_rps(dev_priv->dev, dev_priv->rps.idle_freq);
 		dev_priv->rps.last_adj = 0;
-		I915_WRITE(GEN6_PMINTRMSK, 0xffffffff);
+		I915_WRITE(GEN6_PMINTRMSK,
+			   gen6_sanitize_rps_pm_mask(dev_priv, ~0));
 	}
 	mutex_unlock(&dev_priv->rps.hw_lock);