[coreboot] [Broadwell-U]How the eDP, DDI1, DDI2 are enabled?

[Zheng Bao]

At which stage do you want to enables these ports? in the OS? or during
boot? if the latter, which payload do you use?


Zheng: I want to enable these display port during boot. The payload is SeaBIOS.


Zheng


________________________________
From: Nico Huber <nico.h at gmx.de>
Sent: Saturday, August 5, 2017 12:17 PM
To: Zheng Bao; coreboot at coreboot.org
Subject: Re: [coreboot] [Broadwell-U]How the eDP, DDI1, DDI2 are enabled?

Hi Zheng,

On 04.08.2017 04:35, Zheng Bao wrote:
> I need to clarify my question.
>
> For Broadwell-U, are there internal 3 display ports? Is the first one set
> statically as eDP?

the first (DDI0 or DDI-A) is eDP only. The other two can be used for DP,
HDMI/DVI or both (aka DP++ or dual-mode DP). What you can actually con-
nect depends on your board and the physical connectors of course.

Broadwell-U doesn't provide analog VGA. If your board has a VGA connec-
tor, there's supposedly a converter chip onboard that is either attached
via HDMI or DP to the SoC.

>
> How can these ports be set as other type like VGA, HDMI?

That depends on the software you use. Traditionally, display bringup is
done in a separate program in the firmware (e.g. VGA BIOS, GOP). core-
boot does this as well on most platforms. Also the OS driver should be
able to detect and enable external displays automatically.

At which stage do you want to enables these ports? in the OS? or during
boot? if the latter, which payload do you use?

>
> Can all these 3 ports be enabled at same time?

Yes.

Nico

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