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drm/i915: Use the correct GMCH_CTRL register for Sandybridge+

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The GMCH_CTRL register (or MGCC in the spec) is at a different address
on Sandybridge, and the address to which we currently write to is
undefined. These stray writes appear to upset (hard hang) my Ivybridge
machine whilst it is in UEFI mode.

Note that the register is still marked as locked RO on Sandybridge, so
vgaarb is still dysfunctional.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Chris Wilson 2013-12-17 14:34:50 +00:00 committed by Daniel Vetter
parent be3d26b058
commit a885b3ccc7
1 changed files with 3 additions and 2 deletions
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5
drivers/gpu/drm/i915/intel_display.c
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@ -11126,14 +11126,15 @@ void intel_connector_attach_encoder(struct intel_connector *connector,
int intel_modeset_vga_set_state(struct drm_device *dev, bool state)
{
struct drm_i915_private *dev_priv = dev->dev_private;
unsigned reg = INTEL_INFO(dev)->gen >= 6 ? SNB_GMCH_CTRL : INTEL_GMCH_CTRL;
u16 gmch_ctrl;
pci_read_config_word(dev_priv->bridge_dev, INTEL_GMCH_CTRL, &gmch_ctrl);
pci_read_config_word(dev_priv->bridge_dev, reg, &gmch_ctrl);
if (state)
gmch_ctrl &= ~INTEL_GMCH_VGA_DISABLE;
else
gmch_ctrl |= INTEL_GMCH_VGA_DISABLE;
pci_write_config_word(dev_priv->bridge_dev, INTEL_GMCH_CTRL, gmch_ctrl);
pci_write_config_word(dev_priv->bridge_dev, reg, gmch_ctrl);
return 0;
}