[coreboot] [skylake] Can not turn monitor on

[Zheng Bao]

Sorry for being unclear.

By BIOS stage,  I mean I need to see the text "Press ESC for boot menu." on screen. It also means it needs to boot DOS with display on.
But I can not. I have to wait for the linux to boot. Only Linux (driver?) can turn the display on. I tried with both vbt from github and extracted
from  original AMI BIOS.
My board uses IT6515FN to transfer the display to VGA.

Zheng

________________________________
From: Nico Huber <nico.h at gmx.de>
Sent: Friday, October 5, 2018 8:27 PM
To: Zheng Bao
Cc: coreboot at coreboot.org; youness.alaoui at puri.sm; Matt DeVillier
Subject: Re: [coreboot] [skylake] Can not turn monitor on

On 10/5/18 4:43 PM, Zheng Bao wrote:
> I transfer all the GPIO setting to my code.

What do you mean? did you have wrong GPIO settings before?

> After this, the linux can turn the monitor on, but in BIOS stage,
> monitor can not be turn on.
> Is that the way it is? Can BIOS turn the display on?

What exactly do you mean with BIOS? a VGA BIOS? it should work with the
correct VBT. Same with a GOP driver. I'll add Matt in CC who has more
experience with the proprietary graphics solutions.

Personally, I would just implement the backlight control in coreboot
and use libgfxinit as open-source solution. Register documentation can
be found here [1][2] and soc/intel/broadwell/igd.c:311..344 as example
how it worked on older platforms. Everything else you need are the
correct settings for your board/panel which you can find by decoding
the VBT or just dump the registers when Linux initialized it.

Nico

[1] BLC_PWM_(CTL|DATA) in

https://01.org/sites/default/files/documentation/intel-gfx-prm-osrc-skl-vol02c-commandreference-registers-part1.pdf

[2] PP_* and SBLC_PWM_CTL[12] in

https://01.org/sites/default/files/documentation/intel-gfx-prm-osrc-skl-vol02c-commandreference-registers-part2.pdf
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