builtin display using amdgpu gives a black screen on macbook pro 13, 3

[Alex Deucher]

On Thu, May 7, 2020 at 3:36 PM D Marinus <dmarinus at mrns.nl> wrote:
>
> Hi!
>
> Since I've updated the linux kernel to 5.6 my builtin display of my
> Apple Macbook Pro 13,3 is blank. The following bug reports have been
> opened:
>
> https://github.com/Dunedan/mbp-2016-linux/issues/142
> https://bugzilla.kernel.org/show_bug.cgi?id=207589
> https://bugzilla.redhat.com/show_bug.cgi?id=1829174
>
>
> xrandr gives the following message
> xrandr: Output eDP is not disconnected but has no modes
>
> the /sys/kernel/debug/vgaswitcheroo/switch entry is missing
>
> lspci gives:
> 01:00.0 VGA compatible controller: Advanced Micro Devices, Inc.
> [AMD/ATI] Baffin [Radeon RX 460/560D / Pro
> 450/455/460/555/555X/560/560X] (rev ef)
>
> Any thoughts on the cause or fix? What would be helpful information?

Macs handle hybrid graphics differently than other systems.  Maybe
some change related to the mac mux driver?  A bisection would be
helpful.

Alex