Intel modesetting and tearing

[Jan Beich]

Johannes Lundberg <johalun0 at gmail.com> writes:

> On Thu, Jan 10, 2019 at 18:35 Greg V <greg at unrelenting.technology> wrote:
>
>>
>>
>> On Thu, Jan 10, 2019 at 9:22 PM, Johannes Lundberg <johalun0 at gmail.com>
>> wrote:
>> > On Thu, Jan 10, 2019 at 16:03 Christian Weisgerber
>> > <naddy at mips.inka.de <mailto:naddy at mips.inka.de>>
>> > wrote:
>> >
>> >>  I recently switched from an obsolescent Radeon card to the built-in
>> >>  Intel HD Graphics P4600 with i915kms.ko and the modesetting driver.
>> >>  That works fine, but there is very noticeable tearing whenever
>> >>  something moves on-screen.  If you google for it, you'll find plenty
>> >>  of complaints on Linux, so this is not a FreeBSD issue.
>> >>
>> >>  For MPlayer, replacing the default Xvideo with GL video output (-vo
>> >> gl)
>> >>  eliminates tearing.
>> >>
>> >>  And as I found out just today and quite by accident, in Firefox
>> >>  toggling layers.acceleration.force-enabled to true will also
>> >> eliminate
>> >>  all tearing, whether from soft-scrolling or when playing YouTube
>> >>  videos.  Hallelujah!
>> >
>> >
>> > Woot?! You mean I can use modesetting AND have tearfree Firefox?
>> > Thanks for
>> > the tip!! I will use this until I switch i3 -> Sway.
>>
>> When I still used X on my Intel laptop (of course with the modesetting
>> DDX), I don't think GL acceleration of Firefox helped with tearing. (I
>> always used GL accelerated Firefox anyway.)
>>
>> The solution was fiddling with compton flags, IIRC '--backend glx
>> --vsync opengl-swc' was enough for the Intel GPU
>
>
> What resolution? It’s less noticeable on smaller screens but on 4K at 60Hz
> it’s quite severe and no Compton settings help. I tried them all. Or maybe
> you mean Compton in combination GL in Firefox?

Tearing probably depends on hardware. On my 4K at 60Hz display (LG 27MU67-B
connected to mainboard over DisplayPort 1.2) it isn't as severe, so I'm
using compton *without* --vsync[1]. However, before drm-v4.9 at some point
I had unfixable tearing due to what appeared broken VSync.

--
[1] My config https://github.com/FreeBSDDesktop/kms-drm/issues/32