iMac 10,1 with Ubuntu 16.04: black screen after suspend

[Florian Echtler]

On 31.05.2017 14:57, Alex Deucher wrote:
> On Wed, May 31, 2017 at 5:21 AM, Lukas Wunner <lukas at wunner.de> wrote:
>> On Wed, May 31, 2017 at 10:48:37AM +0200, Florian Echtler wrote:
>>
>> Hm, try booting with drm.debug=0xf to see if link training for the
>> eDP connector succeeds.  If the link cannot be trained, it would
>> explain that the screen stays black.  Should this indeed be the
>> case, one possible explanation would be that the panel is muxed
>> to the external port on resume and an appropriate command needs to
>> be sent to the SMC to switch the mux to the radeon card.  This could
>> be done in the ->resume_early hook of your APP000C platform driver.
>> The apple-gmux driver contains something similar to power the discrete
>> GPU down if it was off before suspend (because the BIOS always powers
>> it up on resume).

Here's the (substantial) dmesg output, with drm.debug=0xf:
http://floe.butterbrot.org/external/radeon/dmesg_after_suspend

I haven't been able to find any references to link training, though.

>> *shrug*  Unfortunately I'm not familiar at all with radeontool. :-(
> 
> You can use the radeonreg tool to dump the display registers:
> https://cgit.freedesktop.org/~agd5f/radeontool/
> radeonreg regs dce3
> replace dce3 with whatever dce version your card has.

AFAICT the RV730 indeed has dce3, so I created a register dump before and after
suspend:
http://floe.butterbrot.org/external/radeon/regs_before_suspend.txt
http://floe.butterbrot.org/external/radeon/regs_after_suspend.txt

The diff, however, is quite large, I have no idea which registers to look for.

Best, Florian
-- 
SENT FROM MY DEC VT50 TERMINAL

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