Intel modesetting and tearing

[Johannes Lundberg]

On 1/10/19 8:17 PM, Greg V wrote:
>
>
> On Thu, Jan 10, 2019 at 9:40 PM, Johannes Lundberg 
> <johalun0 at gmail.com> wrote:
>>
>>
>> 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 <mailto: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> 
>>> <mailto: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?
>
> Yeah, I *always* used GL in Firefox.
>
>
Still no luck...

When running glxgears, scrolling in FF, watching videos (mpv with 
vaapi), etc, I can clearly see a "tear line" something like ascii pic 
below. For normal video playback or FF scrolling it's visible in 4K but 
not (or barely) 1080p. For tear test video playback, it's visible even 
in 1080p.


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