Timeout with USB-C video adapter

Timeout with USB-C video adapter

[Andy Pont]

Hello,

I’m working on the coreboot port for a laptop which uses the N200 
(AlderLake-N).  The built in LCD and HDMI port are working correctly but 
I am having problems with driving an external display over USB.

The Linux kernel (6.5.0-27-generic in Ubuntu 23.10) gives a message that 
says:

i915 0000:00:02.0: [drm] *ERROR* Timeout waiting for DDI BUF D to get 
active

The timeout occurs in hsw_wait_for_power_well_enable().  I have put the 
full dmesg output of the drm_WARN_ON() messages on Pastebin[1].

I’m guessing something in the FSP isn’t being correctly configured but I 
don’t know whether it is graphics, USB, or power related.

Thanks in advance for any advice on where to look.

-Andy.

1. https://pastebin.com/p3JTYpTC

Re: Timeout with USB-C video adapter

[Jani Nikula]

On Wed, 24 Apr 2024, Andy Pont <andy.pont@wonksw.tech> wrote:
> Hello,
>
> I’m working on the coreboot port for a laptop which uses the N200 
> (AlderLake-N).  The built in LCD and HDMI port are working correctly but 
> I am having problems with driving an external display over USB.
>
> The Linux kernel (6.5.0-27-generic in Ubuntu 23.10) gives a message that 
> says:
>
> i915 0000:00:02.0: [drm] *ERROR* Timeout waiting for DDI BUF D to get 
> active
>
> The timeout occurs in hsw_wait_for_power_well_enable().  I have put the 
> full dmesg output of the drm_WARN_ON() messages on Pastebin[1].
>
> I’m guessing something in the FSP isn’t being correctly configured but I 
> don’t know whether it is graphics, USB, or power related.
>
> Thanks in advance for any advice on where to look.

Does it work all right with the stock UEFI boot, and you're only seeing
issues with coreboot?

Is /sys/kernel/debug/dri/0/i915_vbt the same for both?

Might be easier to file a bug as described at [1], and attach full dmesg
with debugs enabled.

BR,
Jani.

[1] https://drm.pages.freedesktop.org/intel-docs/how-to-file-i915-bugs.html


>
> -Andy.
>
> 1. https://pastebin.com/p3JTYpTC
>

-- 
Jani Nikula, Intel

Re: Timeout with USB-C video adapter

[Andy Pont]

Jani wrote...

>Does it work all right with the stock UEFI boot, and you're only seeing
>issues with coreboot?
With the stock UEFI solution (AMI) the USB-C HDMI adapters work booting 
from the same Ubuntu disk.  Interestingly, they don’t work under Windows 
11 with the AMI firmware so I’m not convinced their implementation is 
correct either.

>Is /sys/kernel/debug/dri/0/i915_vbt the same for both?
Yes, the VBT file built into the coreboot firmware is the one I 
extracted from /sys/kernel/debug/dri/0/i915_vbt having booted into 
Ubuntu.

I’ll raise it as a bug (albeit I don’t think it is the driver at fault).

-Andy.