[coreboot] T400 screen issue / EDID handling

[kroms at posteo.be]

Dear Paul,

> As you can see, the vendor firmware detects a dual-link LVDS
> configuration.
> 
> [drm:intel_lvds_init] detected dual-link lvds configuration
> 
> With coreboot a single-link LVDS configuration is detected.
> 
> [drm:intel_lvds_init] detected single-link lvds configuration

Thank you for checking the logs!

> Francis Rowe wrote to the list, that this is configured during compile
> time in coreboot [1][2]. You'd need to rebuild your image. Then you
> should have at least graphics when Linux started.

Yes, I am very happy that they found a workaround. This is the next
thing I am going to do.
Because I re-flashed the Lenovo Bios I have to disassemble the T400
again to reach the flash chip.
I wanted to provide you with the logs first. 

> There are two more things two do.
> 
> 1. Contact the Linux i915 folks and ask them, if the module is able to
> detect the configuration itself and does not rely on the firmware or if
> there is a way to override that setting from the Linux command line.

Who is going to do this? Is this [1 [1]] the right community? I am not
sure, if I am able to explain it right.
If you want me to do this, what do you mean exactly with "the module",
is it "i915"? 

On [2 [2]], is written:
"Linux (kernel) has its own init code (including EDID parsing). The
current suspicion is that coreboot's
own initialization code has buggy EDID parsing in some way, such that
the proper settings for the panel
are not used, leading to the failure."

Please tell me, if I understand it right:
The kernel module should not rely on coreboot concerning the settings
for the display and you want to know, 
if the kernel module is able to get the needed information direct from
the display (EDID)? If this is possible, you want to know,
if this is cofigurable with the Linux command line? Means "Linux command
line" the same as "kernel command line"?

> 2. Improve coreboot so that the LVDS link configuration is detected
> during runtime as the vendor firmware (VGA Option ROM/Video BIOS(?))
> does.

While I am learning a lot of things working on this issue, this is far
above my skills.

Best regards,

Kroms

[1] https://01.org/linuxgraphics/community/kernel
 [1][2] http://libreboot.org/docs/hcl/gm45_lcd.html [2]
 [1]
 

Links:
------
[1] https://01.org/linuxgraphics/community/kernel
[2] http://libreboot.org/docs/hcl/gm45_lcd.html
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