• LINUX
Lenovo Intel i915 Video Drivers in Linux
Note: Out of Date and incorrect analysis.
I’m running fedora 27 on my Lenovo T460s and have been for a while. I have a docking station with two 24" monitors at work and another docking station with two 27" monitors at home. I switch between them frequently. Back in fedora 21 and 22 I had tons of problems. Sometimes monitors didn’t come on, sometimes one monitor came on, and sometimes things worked fine. It got better as of fedora 27, such that I was pretty happy with things. I’m thankful for the hard work put into the video drivers by the people behind fedora, the linux kernel, and the many other distributions contributing.
Something happened recently where things went a little backward. All of a sudden, I was having complete crashes and uncontrolled reboots when moving my laptop from one docking station to another. Maybe it had to do with moving between docking stations. Maybe it just had to do with docking stations in general. I don’t know the details exactly, but here is my own system analysis.
This error had been showing up a lot in my system journal/dmesg, right at the time of crash:
kernel: [drm:intel_ddi_prepare_link_retrain [i915]] *ERROR* Timeout waiting for DDI BUF C idle bit
It apparently started in April with kernel 4.15.9-300.fc27.x86_64:
kernel: Linux version 4.15.9-300.fc27.x86_64 (mockbuild@bkernel02.phx2.fedoraproject.org) (gcc version 7.3.1 20180303 (Red Hat 7.3.1-5) (GCC)) #1 SMP M
A lot of knowledge came from the folks at Arch Linux:
Because they stated "to take advantage of some driver options, you will need to create a Xorg configuration file", I added this to /usr/share/X11/xorg.conf.d/20-intel.conf:
Section "Device"
Identifier "Intel Graphics"
Driver "intel"
EndSectionI also enabled "GuC / HuC firmware loading" in /etc/modprobe.d/i915.conf, since I am on kernel 4.16 now.
options i915 enable_guc=1
What does all this stuff mean? I’m not really sure, but I encourage you to read up on the links if you’re curious. At any rate, it seems like something changed in the i915 driver that was being used for my device. According to a few of these posts, tweaking these driver parameters is helpful. Also, reading the intel(4) man page could be helpful. So far I have not had any crashes, but I will report again if I do. I’m not even sure if the changes I made will really do anything. I might need to update the kernel boot line rather than the modprobe conf.
One day I’ll spend more time on video and graphics. Not today.