Bug 104194 - HDMI with RX460 not working on linux 4.15-rc2 with DC enabled and linux-amd-staging-drm-next
Summary: HDMI with RX460 not working on linux 4.15-rc2 with DC enabled and linux-amd-s...
Status: RESOLVED FIXED
Alias: None
Product: DRI
Classification: Unclassified
Component: DRM/AMDgpu (show other bugs)
Version: XOrg git
Hardware: x86-64 (AMD64) Linux (All)
: high critical
Assignee: Default DRI bug account
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Reported: 2017-12-10 16:13 UTC by laichiaheng
Modified: 2018-02-20 14:46 UTC (History)
4 users (show)

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Description laichiaheng 2017-12-10 16:13:50 UTC 
Graphics: Card: Advanced Micro Devices [AMD/ATI] Baffin [Radeon RX 460/560D / Pro 450/455/460/560] 
Display Server: x11 (X.Org 1.19.5 ) driver: amdgpu Resolution: 1920x1080@60.00hz 
OpenGL: renderer: AMD Radeon RX 460 Graphics (POLARIS11 / DRM 3.23.0 / 4.15.0-rc2-mainline, LLVM 6.0.0) 
version: 4.5 Mesa 17.4.0-devel (git-4c7af87fb9)


GRUB_CMDLINE_LINUX_DEFAULT="quiet amdgpu.dc=1"


Nothing is output to the HDMI when amdgpu.dc is enabled
Comment 1 laichiaheng 2017-12-11 08:31:21 UTC 
I've found a solution to make it work, just re-plug-in the HDMI cable from the GPU side (not the screen side)
Comment 2 Jerry Zuo 2017-12-19 15:59:35 UTC 
(In reply to laichiaheng from comment #1)
> I've found a solution to make it work, just re-plug-in the HDMI cable from
> the GPU side (not the screen side)

I've checked the top of the amd-staging-drm-next(59b8f814a) but don't see the issue. 4K HDMI display connected on Baffin could light up. Please check it as well, and see if the issue still exists.

Please also let me know which build you have used to have this issue reproduced. Thanks.
Comment 3 saunders.52 2018-02-06 19:08:19 UTC 
I am having this issue as well on 4.15.1 without DC enabled (as well as DC enabled) on a RX 460. Will try the cable replug on GPU side (didn't work on monitor side.)
Comment 4 saunders.52 2018-02-06 19:17:26 UTC 
Unplugging and replugging the cable on the GPU side causes the monitor to be detected without DC enabled. (Haven't checked with DC.)
Comment 5 saunders.52 2018-02-20 04:49:02 UTC 
Is there any info that would be useful to provide in order to help debug this issue? It's occurring on a stable build for me, unlike the other person with this problem.
Comment 6 Jordan L 2018-02-20 08:36:57 UTC 
Hi,

Would you mind posting your dmesg and X logs while the monitor is black?

Does the monitor show up as enabled on xrandr?

Thanks
Comment 7 saunders.52 2018-02-20 09:07:41 UTC 
(In reply to Jordan L from comment #6)
> Hi,
> 
> Would you mind posting your dmesg and X logs while the monitor is black?
> 
> Does the monitor show up as enabled on xrandr?
> 
> Thanks

Um... I can't replicate anymore. The bug triggered reliably on Arch for me on 4.15.1, but Arch has since updated to 4.15.3 and this has... somehow caused the card to start recognizing the HDMI card on boot (in non-DC mode when I just booted it, twice). I'd been using the 4.14 series of LTS kernels in the meantime, and none of the changes had seemed to indicate anything that would fix it in the 4.15.x point releases...
Good work, I guess. Sorry about the wasted time, if it occurs again (it triggered a bunch for me on a few days after 4.15.x came out) I'll post the logs.
Comment 8 saunders.52 2018-02-20 09:16:26 UTC 
Hmm... going by Arch Linux package differences, the dmesg output, and the fact I suddenly have working HDMI support, they seem to have set AMDGPU DC to be on by default now on the 4.15 kernels for pre-Vega cards without a command line setting, which might have something to do with it.

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