Fixing the Freeze (Latitude 7490)

Sep 15, 2022 i915 dell latitude 7490 freeze hang

TL;DR Disable i915 graphics module to stop freezes in Ubuntu on a Latitude 7490

I recently swapped out my day-to-day personal Dell XPS laptop for a similarly specced Dell Latitude, the 7490 with an i7-8650 CPU and “Mesa Intel® UHD Graphics 620 (KBL GT2)”. The change was driven by a combination of diminishing battery life, the lack of any ports other than USB C on the XPS, and the opportunity to beef up the memory.

The official Dell specs for this laptop says that it can accommodate a maximum of 32 GiB, but it seems that this was a limitation of the SODIMMs available when it was current - and indeed I have now populated it with 64 GiB.

With a nice 2TB nvme drive and Ubuntu 22.04.1 LTS installed, everything was looking good - however I started to get intermittent hangs - screen frozen, keyboard and mouse inactive, no access via network. I’d say they were occurring roughly once every 48 hours, but irregularly, so I would see perhaps two on one day, then none for several.

Initially I feared that the extra memory was causing problems. Although initial googling found only a few issues with damaged hardware or improperly seated memory, I eventually found the solution in an Ubuntu bug thread where they recommend disabling the Intel i915 (graphics) module. This has completely cured the problem for me, so it’s definitely worth trying:

Edit /etc/default/grub to add the boot parameter i915.enable_dc=0 - so, for me, this changes line 10 in that file from this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

To this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.enable_dc=0"

You’ll then need to run sudo update-grub to apply the change to grub and reboot to pick it up.

There are some other options discussed in that bug thread, so you might want to read it in full if you have need of the capabilities of that module - my graphics demands are low to non-existent, however, and I see no practical difference after the change.