[Bug 48652] [IVB CPU eDP] local flat panel stays blank, workaround: intel_iommu=igfx_off

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=48652

--- Comment #117 from Chris Wilson <chris at chris-wilson.co.uk> ---
(In reply to comment #107)
> So, i tasted with latest git 3.10.0-rc7-00854-gf19c9d3 - same result.
> 
> (gdb) l *intel_crtc_set_config+0x216
> 0x2bab0 is in intel_crtc_set_config
> (/home/lex/tmp/linux/drivers/gpu/drm/i915/intel_display.c:8678).
> 8673			      int num_connectors)
> 8674	{
> 8675		int i;
> 8676	
> 8677		for (i = 0; i < num_connectors; i++)
> 8678			if (connectors[i].encoder &&
> 8679			    connectors[i].encoder->crtc == crtc &&
> 8680			    connectors[i].dpms != DRM_MODE_DPMS_ON)
> 8681				return true;
> 8682	
> 
> 
> I noticed that in some circumstances i null pointer dereference on xhci
> driver. Interesting, are these errors connected? Or may be there is some
> memory region used by what ever, bios, efi?

This OOPS is fixed by

commit 2e57f47d317dd035b18634b0c602272529368fcc
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Wed Jul 17 12:14:40 2013 +0100

    drm/i915: Fix dereferencing invalid connectors in is_crtc_connector_off()

    In commit e3de42b68478a8c95dd27520e9adead2af9477a5
    Author: Imre Deak <imre.deak at intel.com>
    Date:   Fri May 3 19:44:07 2013 +0200

        drm/i915: force full modeset if the connector is in DPMS OFF mode

No idea why VT-d affects that at all.

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