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Old 10-30-2015, 05:10 PM   #4
xenith
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Join Date: Oct 2015
Posts: 6
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Ok speculation time -

I had this issue at one point in my initial purchasing of this hardware which was when I wrote this:

http://displaylink.org/forum/showthr...8712#post78712

I had made the assumption that the CPU usage was otherwise normal (mine was a little lower but still _very_ high) for driving two screens.

For curious testing purposes I installed windows on a USB hard drive, booted that, and installed the proper displaylink drivers for windows 8.1 on that. Low and behold... It was capable of driving not two, but _3_ 1080p screens with zero lag over 1 USB3 port with relatively little CPU usage. This surprised me due to the poor performance I was seeing on Linux.

Point being, the hardware is capable. It's the failure of this company to produce Linux drivers that work as well that cause our pain and suffering.

Now, the reason that I'm writing this post -

Strangely, when I booted back into Fedora 22, I noticed that the lag wasn't present anymore (the screens no longer felt like they were clocked at 30Hz when they were previously) and the CPU usage was decreased dramatically.

I'm not sure whether or not I had a lingering kernel upgrade in between, but my speculation is that the windows drivers properly updated the firmware on the device itself, where the Linux drivers didn't. So, as a potential 'fix' attempt to find a windows computer that you can plug it into first.

Unfortunately, again, whether it's the latest kernel or the firmware that was upgraded on the device, I don't know. But there are a whole other host of issues that come from whatever upgrade happened, too. For some reason, unlike before, the devices fails ungracefully if X is ever restarted and gives the following error message until the computer is rebooted:

[ 453.842446] [drm:check_crtc_state [i915]] *ERROR* mismatch in ips_enabled (expected 1, found 0)
[ 453.842633] [drm:check_crtc_state [i915]] *ERROR* mismatch in ips_enabled (expected 1, found 0)

It's as if something isn't being released properly.
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