Re: [PATCH] drm/i915/ddi: Fix default eDP detection on port A

From: Thomas Preston
Date: Thu Mar 07 2019 - 05:02:25 EST

Thanks for looking at this.

On 07/03/2019 08:18, Jani Nikula wrote:

The subject should probably have "drm/i915/bios" or "drm/i915/vbt".


On Wed, 06 Mar 2019, Thomas Preston <thomas.preston@xxxxxxxxxxxxxxx> wrote:
We rely on VBT DDI port info for eDP detection on GEN9 platforms and
above. This breaks GEN9 platforms which don't have VBT because port A
eDP now defaults to false. Fix this by defaulting to true when VBT is

Please include more details about the machine that doesn't have VBT. Why
don't you have VBT?

We have upgraded from an earlier kernel version (an Intel BSP on v4.1)
which did not require VBT and so our BIOS isn't set up correctly. The
BIOS doesn't set ASLS and fails to find ACPI OpRegion:

[ 9.368433] [drm:intel_opregion_setup [i915]] graphic opregion physical addr: 0x0
[ 9.368490] [drm:intel_opregion_setup [i915]] ACPI OpRegion not supported!

So now our port A is DP instead of eDP. I was hoping a return to "default"
values would remedy this, but I think it's pretty clear now that we should
focus on fixing VBT.

I've found a default VBT in the BSP but not sure how to get it into BIOS.
If you could point me in the right direction here that would be really

Personally I think it was a mistake originally to make guesses about the
outputs in absence of VBT on DDI platforms, because we can never get the
generic guesses right across all ports and all products. And for the
record, that was the result of an easy choice to enable developers way
back when, and forgotten.

Certainly eDP is more likely than something else on port A. But this
will break any outlier products without VBT that have a non-eDP output
on port A. I guess it's a risk we have to take, and handle the fallout

Acked-by: Jani Nikula <jani.nikula@xxxxxxxxx>

Fixes: commit a98d9c1d7e9b ("drm/i915/ddi: Rely on VBT DDI port info for eDP detection")

The Fixes: format does *not* include "commit" text.

I got that from scripts/ but noted, thanks.

Kind regards,