Bug 99744

Summary: Bad crtc detection on Radeon Pro WX 4100
Product: DRI Reporter: Matt Corallo <freedesktop>
Component: DRM/AMDgpuAssignee: Default DRI bug account <dri-devel>
Status: RESOLVED FIXED QA Contact:
Severity: normal    
Priority: medium CC: freedesktop
Version: unspecified   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
Xorg.log
none
dmesg grep amd, drm, dmar (in case its relevant)
none
xrandr --verbose
none
possible fix none

Description Matt Corallo 2017-02-09 20:27:57 UTC 
Radeon Pro WX 4100 specs quoted from an AMD press release upon announcement seem to indicate that it is capable of driving 4 4k monitors, however, xrandr/Xorg will only allow it to drive 2 monitors at any one time (irrespective of configured resolution).

xrandr --verbose lists each of the 4 MiniDP ports as "CRTCs: 0 1" and xrandr --listproviders lists "Provider 0: id: 0x58 cap: 0xf, Source Output, Sink Output, Source Offload, Sink Offload crtcs: 5 outputs: 4 associated providers: 0 name:POLARIS11 @ pci:0000:81:000".

Kernel 4.9.8

(haven't tested on Windows or anything else as those are generally not available to test on this machine).
Comment 1 Michel Dänzer 2017-02-10 01:39:39 UTC 
Please attach the Xorg log file and dmesg output corresponding to the problem.

This is up to the kernel driver. You could try the amd-staging-4.9 branch of https://cgit.freedesktop.org/~agd5f/linux/ with CONFIG_DRM_AMD_DC enabled to see if that works better.
Comment 2 Matt Corallo 2017-02-10 02:30:47 UTC 
Created attachment 129461 [details]
Xorg.log
Comment 3 Matt Corallo 2017-02-10 02:33:32 UTC 
Created attachment 129462 [details]
dmesg grep amd, drm, dmar (in case its relevant)
Comment 4 Matt Corallo 2017-02-10 02:34:48 UTC 
Attached (possibly) relevant logs. Will test on the staging branch when I get a chance (probably in a week or two). I figured the issue would be with the kernel driver but didnt see an obviously better place to file a bug, should I have filed on kernel bugzilla?
Comment 5 Michel Dänzer 2017-02-10 02:46:42 UTC 
This bugzilla is preferred for kernel driver issues as well. I reassigned this report to the correct product and component.

Can you also attach the output of xrandr --verbose?
Comment 6 Matt Corallo 2017-02-10 03:10:44 UTC 
Created attachment 129463 [details]
xrandr --verbose
Comment 7 Alex Deucher 2017-02-10 05:03:44 UTC 
Created attachment 129464 [details] [review]
possible fix

This patch should fix the issue.
Comment 8 Matt Corallo 2017-02-19 01:33:37 UTC 
Confirmed the attached patch fixes the issue.
Comment 9 Matt Corallo 2017-04-07 12:45:29 UTC 
Fixed in stable/LTS/mainline.

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