From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Fri, 7 Feb 2014 20:37:03 +0000 (-0200)
Subject: drm/i915: Short-circuit no-op vga_set_state()
X-Git-Tag: firefly_0821_release~176^2~4105^2~59^2~54
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=c0cc8a556680afbfc6dc5033bdf9c8d2b85088e2;p=firefly-linux-kernel-4.4.55.git

drm/i915: Short-circuit no-op vga_set_state()

Touching the VGA registers risks a hard machine hang, at least on this
ivb machine after removing a conflicting efifb. This is more than likely
related to the discovery that VGA IO decode on the more recent PCH
platforms is terminally broken.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index cc426e10d746..1b2faa44764b 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -11513,6 +11513,9 @@ int intel_modeset_vga_set_state(struct drm_device *dev, bool state)
 		return -EIO;
 	}
 
+	if (!!(gmch_ctrl & INTEL_GMCH_VGA_DISABLE) == !state)
+		return 0;
+
 	if (state)
 		gmch_ctrl &= ~INTEL_GMCH_VGA_DISABLE;
 	else