apparent workaround for i915 "black screen" issue

[Robert P. J. Day]

  i'm fairly sure some folks here are at least aware of the recent
intel intergrated graphics i915 issue that produced a totally black
screen upon booting, even though the system quite clearly booted.

  after swapping numerous posts on the intel free desktop mailing list
and getting piles of guidance from chris wilson, i isolated a
workaround to applying this simple patch:

diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c
index 64fd644..28adc6d 100644
--- a/drivers/gpu/drm/i915/intel_opregion.c
+++ b/drivers/gpu/drm/i915/intel_opregion.c
@@ -495,6 +495,8 @@ int intel_opregion_setup(struct drm_device *dev)
                opregion->acpi = base + OPREGION_ACPI_OFFSET;
        }

+return 0; // rday
+
        if (mboxes & MBOX_SWSCI) {
                DRM_DEBUG_DRIVER("SWSCI supported\n");
                opregion->swsci = base + OPREGION_SWSCI_OFFSET;


  i isolated the workaround to this file using "git bisect", then used
chris' advice to return earlier than normal to see which of those
conditional snippets was causing the problem.

  i won't pretend to know what's going on there, but if anyone else is
seeing the i915-related black screen issue and wants to test the
above, it would be nice to verify that this workaround works for
someone else.

rday

-- 

========================================================================
Robert P. J. Day                               Waterloo, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================