Thanks Nico.

HPD is active , measured the signal

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)

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,

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?

Regards

Rao

On Fri, Jul 30, 2021 at 4:49 PM Nico Huber <nico.h@gmx.de> wrote:

Hi,

On 30.07.21 16:47, Rao G wrote:
> The problem originally I had was that on PortC, DP/HDMI did not work for
> the external display in the OS, In BIOS it looked good,
> so I configured PortC as an eDP interface then the external display started
> working in the OS.

this sounds much like you are still facing the same problem. When you
configure the port as eDP, Linux' i915 will simply skip reading the
exact register we are looking (and just assume the display is present).

Have you tried to measure the hotplug signal when your display is
connected/disconnected? Maybe something is physically wrong with the
board design, cable, or display?

Nico