Tonga Kernel Modesetting Issue

Alex Deucher alexdeucher at
Mon Apr 2 19:21:40 UTC 2018

On Mon, Apr 2, 2018 at 10:29 AM, Ian Bashford <ianbashford at> wrote:
> Hi,
> I'm investigating an issue with KMS on my graphics card. I'm hoping this
> list might give me some direction/guidance where to look.
> Sometime in between kernels 4.9 and 4.14, the KMS on my card stopped getting
> set to 2560x1440 and only sets 1920x1080.  Passing video= as a kernel
> parameter just leads to a black screen.
> I've tried stock kernels on alpine and arch, and also compiled a few as
> well; I can't see any obvious differences in the compile options that might
> lead to the difference.
> My next line of enquiry is to see if there's a change in amdgpu that might
> be the cause.
> Given the size of the codebase and the number of changes, I was hoping
> someone might be able to help me narrow the possible search.
> Would you be able to suggest somewhere to begin ?

If you can try a newer kernel (4.16 or 4.17rc), try enabling the new
dc modeseting code (append amdgpu.dc=1 on the kernel command line in

What type of display (DVI, DP, etc.) is your monitor and what physical
connector is it connected to on your board?  Are there any adapters
between the card and the display?  Probably best to file a bug
( and attach your xorg log and dmesg
output in both the working and non working cases.

The best way to sort this out would be to use git to bisect what
commit caused the issue.


> The card is a Sapphire R9 380X NITRO 4GB  - it identifies as a TONGA.
> During the boot, I get this message about the mode setting
> [drm] initializing kernel modesetting (TONGA 0x1002:0x6938 0x174B:0xE308
> 0xF1)
> thanks
> Ian
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