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#1 2016-06-10 16:34:31

andytoshi
Member
Registered: 2016-06-10
Posts: 6

No 4K support after upgrading 4.6.1 - 4.6.2

Possibly related: https://bbs.archlinux.org/viewtopic.php?pid=1633511 which describes a few problems with Intel HW on the 4.6 series.

I'm using a Thinkpad 440p with Intel built in graphics. Output of lshw is

[root@titanic ~]# LANG=en_US lshw -class display
  *-display                 
       description: VGA compatible controller
       product: 4th Gen Core Processor Integrated Graphics Controller
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 06
       width: 64 bits
       clock: 33MHz
       capabilities: msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:31 memory:f0000000-f03fffff memory:e0000000-efffffff ioport:3000(size=64) memory:c0000-dffff

After upgrading from 4.6.1-2 to 4.6.2-1 I found that my external monitor no longer supports 4K; the 3840x2160 mode no longer appears in xrandr output and I can't use it ("cannot find mode"). I'm stuck at HD. Downgrading the kernel fixes this.

My external monitor is connected by a cheap Amazon Basics MiniDP->HDMI converter; the product description claims it only supports 1920x1080 but I've been using it with 4K for months now without any trouble.

Has anyone else seen similar behaviour? Are there any workarounds? The thread I linked at the beginning of this post hints that the 4.7 kernels will have some fixes for Intel graphics hardware-related issues, but it seems like this is a new one.

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#2 2016-06-13 14:53:53

benghaem
Member
Registered: 2015-02-03
Posts: 3

Re: No 4K support after upgrading 4.6.1 - 4.6.2

I have also experienced this same behaviour on a Thinkpad T440s with Intel built-in graphics.  4K output in Windows is completely functional which removes possible hardware failure. I also attempted to manually add the required 4K modes after generating the modeline with CVT, but they fail to apply when running xrandr --output.

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#3 2016-06-13 20:11:35

BuZZ-dEE
Member
Registered: 2015-10-14
Posts: 6

Re: No 4K support after upgrading 4.6.1 - 4.6.2

I have this problem too and I also downgraded to linux 4.6.1-2.

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#4 2016-06-28 22:39:21

benghaem
Member
Registered: 2015-02-03
Posts: 3

Re: No 4K support after upgrading 4.6.1 - 4.6.2

Update: I upgraded to 4.6.3-1 with the hope that the problem would be solved, but 1080p remains the highest detected resolution.

Last edited by benghaem (2016-06-28 22:39:40)

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#5 2016-12-11 14:48:32

BuZZ-dEE
Member
Registered: 2015-10-14
Posts: 6

Re: No 4K support after upgrading 4.6.1 - 4.6.2

Update: I upgraded to 4.8.12-3 with the hope that the problem would be solved, but 1080p remains the highest detected resolution.

Last edited by BuZZ-dEE (2016-12-11 15:14:14)

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#6 2016-12-11 15:26:27

seth
Member
Registered: 2012-09-03
Posts: 8,919

Re: No 4K support after upgrading 4.6.1 - 4.6.2

> the product description claims it only supports 1920x1080

Well...
The key is probably in the modeline you created. First, check the xorg log whether any preferred (but unused) modelines/parameters are listed for the desired resolution.
Second, you'll *very* likely have to use a modeline with reduced blanking, possibly 30fps, to get anywhere.

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#7 2018-01-25 23:32:18

BuZZ-dEE
Member
Registered: 2015-10-14
Posts: 6

Re: No 4K support after upgrading 4.6.1 - 4.6.2

I upgraded to 4.14.15-1 with the hope that the problem would be solved now, but 1080p remains the highest detected resolution.

What can I do to correct the resolution?

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#8 2018-01-26 00:32:07

ooo
Member
Registered: 2013-04-10
Posts: 1,607

Re: No 4K support after upgrading 4.6.1 - 4.6.2

man git-bisect

Since you already know the issue was introduced between 4.6.1 and 4.6.2, it shouldn't take too long

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#9 2018-01-26 00:44:40

loqs
Member
Registered: 2014-03-06
Posts: 6,377

Re: No 4K support after upgrading 4.6.1 - 4.6.2

ooo wrote:

Since you already know the issue was introduced between 4.6.1 and 4.6.2, it shouldn't take too long

There will be at least one issue introduced with the switch to gcc7 you should be able to find the relevant patch from a search engine query of the build error you encounter.

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