[Bug 105549] Black/blank screen at boot (last message line: fb: switching to inteldrmfb from EFI VGA) unless i915.modeset=0 is set

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=105549

Ville Syrjala <ville.syrjala at linux.intel.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |NEEDINFO

--- Comment #19 from Ville Syrjala <ville.syrjala at linux.intel.com> ---
[   35.442022] [drm:intel_dp_init_connector [i915]] using AUX C for port C
(VBT)
[   35.442038] [drm:intel_hdmi_init_connector [i915]] Adding HDMI connector on
port C
[   35.442052] [drm:intel_hdmi_init_connector [i915]] Using DDC pin 0x2 for
port C (VBT)
...
[   35.461411] WARN_ON(!intel_gmbus_is_valid_pin(dev_priv, pin))
...
[   35.461609] BUG: unable to handle kernel NULL pointer dereference at
0000000000000010
[   35.461613] IP: i2c_transfer+0x4/0x86

So the VBT has a bogus gmbus pin specified for some reason. 2==VGADDC and
indeed that doesn't appear in the skl valid pins list. And the spec agrees with
our list.

Please attach a copy of /sys/kernel/debug/dri/0/i915_vbt.

I wonder if we should perhaps reject the entire HDMI port when the gmbus pin is
bogus? We'd lose one the HDMI ports though. Also these machines seem to have
eDP + HDMI + DP via type-C + VGA on them. I wonder how it's all hooked up when
we have just three ports declared in the VBT...

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