[PATCH 5/9] drm/i915: Short-circuit no-op vga_set_state()

Rodrigo Vivi
2014-02-07T20:37:30Z

From: Chris Wilson <chris@chris-wilson.co.uk>

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>
---
drivers/gpu/drm/i915/intel_display.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 1e9dd84..c411bf8 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -11575,6 +11575,9 @@ 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
--
1.8.3.1

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