Thank you Matt.

the VBT data in BIOS and VBT data captured in OS if they remain identical would that mean this problem

is not due to VBT data copied into ACPINVS igd_opregion?

Attaching VBT data for this platform which is captured from OS

also Xrandr output on each Video Interface 

On Wed, Aug 11, 2021 at 3:28 PM Matt DeVillier <matt.devillier@gmail.com> wrote:

On Wed, Aug 11, 2021 at 5:05 AM Rao G <grao.v80@gmail.com> wrote:
>
> Thanks Nico for your response.
>
> > am expecting some register should set with eDP as interface and when
> > display is connected
> >
> > any clue why the i915 OS driver was turning off DP display in case 2?
> I assume the HPD signal doesn't get through to the software.
>
> [Rao]
> You mean I need to check PORT_HOTPLUG_EN and PORT_HOTPLUG_STAT mmio offsets for this issue?
> BIOS display is fine, Windows logo is also seen but there is no signal when "windows login" is reached

IME, that's almost always due to incorrect/missing/mismatched VBT data
in the ACPI opregion/mailbox

>
> It had similar behaviour w.r.t to ubuntu 18.04, I configured DDI1 to "DP with HDMI/DVI"
>
> Can this issue be fixed with VBE data configured through BMP or it needs a fix from graphics MMIO?
>
> Regards
> Rao
>
> On Fri, Jul 30, 2021 at 10:27 PM Nico Huber <nico.h@gmx.de> wrote:
>>
>> On 30.07.21 18:59, Rao G wrote:
>> > Thanks Nico.
>> >
>> > HPD is active , measured the signal
>>
>> Is your coreboot port public somewhere? If the hardware is fine, maybe
>> the firmware isn't?
>>
>> >
>> > Configured Ports
>> > 1.DDI0- PortB - DP with HDMI/DVI is good in BIOS & OS
>> > 2.DDI1- PortC - DP with HDMI/DVI is good in BIOS, i915 was turning off the
>> > DP display (Never understood the reason)
>>
>> It's very suspicious that these two behave differently. Does the HPD
>> signal (MMIO read) work for DDI0?
>>
>> >
>> > So configured PortC with eDP
>> >
>> > If there is no way BIOS to detect the external display with MMIO registers
>> > when configured as eDP, Can i not turn off the DDI1/Port C at runtime in
>> > BIOS,
>>
>> Maybe it's time to switch to an open-source solution? libgfxinit will
>> probably have the same issue, but it might be possible to get a rather
>> short delay.
>>
>> > am expecting some register should set with eDP as interface and when
>> > display is connected
>> >
>> > any clue why the i915 OS driver was turning off DP display in case 2?
>>
>> I assume the HPD signal doesn't get through to the software.
>>
>> Nico
>
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