[coreboot] Re: Display Port Monitor turns off during Ubuntu OS boot

[Rao G]

Hi Mike,

Yes the platform uses coreboot, the display is fine in BIOS
only in the OS ubuntu it turns off

Is it required to dump the graphics registers in OS through intel-gpu-tools?
https://01.org/sites/default/files/documentation/intel_os_gfx_prm_vol10_-_di...

Anyone come across similar behavior with display port?
HDMI, LVDS, DVI all works well

Thanks
Rao

On Tue, Mar 2, 2021 at 3:29 PM Mike Banon  wrote:
> Is your platform coreboot-supported, if yes - have you tested it with
> coreboot?
>
> On Thu, Feb 25, 2021 at 9:09 PM Rao G  wrote:
> > Hi Coreboot Team,
> >
> > There is an external Monitor which works on HDMI/DVI and also DP , In
>
> BIOS the display is good whereas in OS (Ubuntu 18.04) until the kernel is
> initialized and i915 Video driver
> > is loaded display is perfect, looks like the i915 OS driver switches off
>
> the monitor and there is no signal
> > Does ACPI GFX method have to return any External display specific data
>
> to the OS driver ?
> > Tried to make changes to VBIOS but did not help, thought ASL code is
>
> missing under GFX0
> > From the OS following data can be read
> >
> > External Monitor's EDID data can be read from I2C Bus
> > Even VBT data from ACPI NVS can be read
> >
> > Tried to dig into some of these files
>
> https://github.com/torvalds/linux/tree/master/drivers/gpu/drm/i915/display
> > intel_dp.c, intel_acpi.c to understand what function is turning off DP
>
> link
> > when i have the OS debug driver logs, can send it across
> >
> > Any clues will help, appreciate your time
> >
> > PS:The platform has Intel BayTrail SoC, ValleyView chipset and VBIOS.
>
> The bios do not use GOP driver which replaces VBIOS
> > Thanks
> > Rao
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