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May 2017
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airlied [userpic]
radeon display port working

Finally got some time to take another look at radeon displayport support.

I wrote initial userspace modesetting patches in June to get EDID and by mid July I had it to the stage where I could
get a display if I started X, then used xrandr to switch to a different mode. I ran out of time to continue investigations then.

Last week Alex Deucher rebased my code into the latest DDX and cleaned up a lot of the insanity in it. At the same time I started porting the code to the kernel for KMS support. Alex also picked that up and made the userspace and kernel drivers pretty much act the same. However at the end of this neither of us actually had reliable display port support.

So this morning I discovered that actually every second modeset was working, with ones in between turning off power to the monitor, so I moved a few things around in the displayport link training initialisation code and voila reliable userspace displayport. I then ported the same fix to the kernel and it didn't make it work. Another 2-3 hours of guessing found a missing
return statement which meant we ended up with a version 0 DP identification which broke stuff. With that fixed, KMS displayport started working.

Where can I get this?
UMS/DDX: git://git.freedesktop.org/git/xorg/driver/xf86-video-ati displayport branch
KMS: git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6.git drm-radeon-dp branch

a) When r600 grows IRQ support we need to use the hotplug irq to detect the monitor appearing/disappearing
so we can retrain the link with it, otherwise unplugging the monitor means it won't be there on replug,
unless you change modes, for userspace we probably need to use a timer to detect if the monitor goes away or we lose
b) cleanup code, maybe see what we can share with Intel.
c) merge, I'd say we can nearly merge the UMS code to master, and KMS can definitely go in the next merge window.

[updated for pedants].


Very nice done =)