Intel Skylake Multi-Screen Issues On Linux Still Happening

While Intel Skylake hardware has been available for one year now, various issues persist for Linux desktop users wishing to make use of Skylake graphics on Intel's open-source Linux driver.

It seems that Skylake has arguably surpassed Sandy Bridge as the worst Intel Linux driver support at launch-time with the various Skylake troubles persisting one year later. While Ivy Bridge, Haswell, and Broadwell all seemed to have gone smoothly and with good day-one support, Skylake has been much a different story.

I personally haven't tried Skylake multi-monitor support in a while and back then it didn't go too well. This weekend I was alerted to a Phoronix reader that Skylake's multi-monitor support on Linux is still in bad shape, including for laptops connected to an external display.

Various documented bugs are outstanding concerning Intel Skylake graphics on Linux when it comes to multi-monitor handling, screen flickering, black screens, pipe under-runs, hard freezes, and more. While Intel has many developers on their open-source graphics team, even Red Hat has resorted to working on some of the issues around multi-monitor handling.

Since the watermark calculations for Skylake are still broken, we're apt to hitting underruns very easily under multi-monitor configurations. While it would be lovely if this was fixed, it's not. Another problem that's been coming from this however, is the mysterious issue of underruns causing full system hangs. An easy way to reproduce this with a skylake system:

- Get a laptop with a skylake GPU, and hook up two external monitors to it
- Move the cursor from the built-in LCD to one of the external displays as quickly as you can
- You'll get a few pipe underruns, and eventually the entire system will just freeze.

Ouch. Many Skylake Linux bugs appear related to the watermark calculations code, which as of Linux 4.8 hasn't been fixed.

This Phoronix reader also pointed out to me a firmware-related power consumption regression currently present in Linux 4.8. See this bug report about silly firmware breakage.

I'll be running some fresh Skylake tests soon from Linux 4.8 + Mesa 12.1 Git. It's all Skylake desktop hardware that I've had for the past year with unfortunately no SKL mobile devices, which may be why I haven't been seeing some of these issues. My main Fedora 23 production system is powered by HD Graphics 530 connected to a single 4K display and at least there it continues going well. How's your Skylake experience been on Linux? Share your thoughts by commenting on this article in the forums.