Re: DisplayPort not working on 11th gen i7 / UHD Graphics 750

[Eduardo M KALINOWSKI <eduardo@kalinowski.com.br>]

On 17/08/2021 15:12, Andrew M.A. Cater wrote:
> On Tue, Aug 17, 2021 at 01:18:11PM -0300, Eduardo M KALINOWSKI wrote:
> > I've installed Debian testing on a new computer, with an Intel Core i7-11700
> > processor.
> >
> > After I added "i915.force_probe=4c8a" to the kernel command-line, graphics
> > work, but only on the HDMI port. A second monitor in the DisplayPort is not
> > recognized:
> >
> > $ xrandr
> > Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 16384 x 16384
> > HDMI-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y
> > axis) 477mm x 268mm
> >     1920x1080     60.00*+  50.00    59.94
> >     1920x1080i    60.00    50.00    59.94
> >     1680x1050     59.88
> >     1280x1024     75.02    60.02
> >     1440x900      74.98    59.90
> >     1280x960      60.00
> >     1280x720      60.00    50.00    59.94
> >     1024x768      75.03    60.00
> >     800x600       75.00    60.32
> >     720x576       50.00
> >     720x576i      50.00
> >     720x480       60.00    59.94
> >     720x480i      60.00    59.94
> >     640x480       75.00    72.81    66.67    60.00    59.94
> >     720x400       70.08
> > DP-1 disconnected (normal left inverted right x axis y axis)
> > HDMI-2 disconnected (normal left inverted right x axis y axis)
> >
> > The cable and monitor are working fine. Dual screens work on Grub and in the
> > beginning of boot, but once the console font changes, I only get HDMI
> > output.
> >
> > Some more information:
> >
> > $ uname -a
> > Linux gandalf 5.10.0-8-amd64 #1 SMP Debian 5.10.46-4 (2021-08-03) x86_64
> > GNU/Linux
> >
> > $ inxi -G
> > Graphics:  Device-1: Intel RocketLake-S GT1 [UHD Graphics 750] driver: i915
> > v: kernel
> >             Display: x11 server: X.Org 1.20.11 driver: loaded: modesetting
> > unloaded: fbdev
> >             resolution: 1920x1080~60Hz
> >             OpenGL: renderer: Mesa Intel Graphics (RKL GT1) v: 4.6 Mesa
> > 20.3.5
> >
> > $ lspci -k -nn -d 8086:4c8a
> > 00:02.0 VGA compatible controller [0300]: Intel Corporation RocketLake-S GT1
> > [UHD Graphics 750] [8086:4c8a] (rev 04)
> >          DeviceName: Onboard - Video
> >          Subsystem: ASUSTeK Computer Inc. Device [1043:8694]
> >          Kernel driver in use: i915
> >          Kernel modules: i915
> >
> > Anyone has any idea? Or is there any extra information that might be useful?
> If you installed Testing in the run up to Bullseye release on 20210814, can
> I suggest that you retry with the installer that was released as the
> final Debian 11 media. The kernel changed in the last few days, it's only
> a small thing but might make a difference.

I actually installed with debootstrap, to run root on zfs. I believe I 
have the latest kernel avaliable (linux-image-5.10.0-8-amd64), I see no 
updates.

> Do you have firmware installed?

Yes, I have firmware-misc-nonfree which is necessary for graphics. As I 
said, everything seems to be working fine, even hardware acceleration, 
but only one monitor is recognized.

It might be that this hardware is too new. (I did need to add one 
parameter to the i915 driver to have any graphics at all.)