[Bug 106191] FirePro v8800 Failure to recognize DisplayPort signal

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=106191

--- Comment #11 from François Jacques <francois.jacques at gmail.com> ---

The bug is caused by having both the audio signal and image simultaneously, it
seems. 

After I added "radeon.audio=0" to the kernel argument list and rebooted, the
video interface and the monitor concluded their signal handshake successfully
(!) and I could switch the monitor to full res and, lo' behol',  a 1440p image
(!!).

For future reference, should anyone have issues, try radeon.audio=0. If you
were relying on the radeon for audio, look for an alternative, or use a
DP-to-HDMI adapter and tolerate the lower resolution until the bug is fixed.

----

Googling on this specific symptom revealed multiple regressions on this matter
before, it could be a new one or it's been lurking for a while. Which means
either:
- tons of dupes in the DRM bugs list wrt radeon and DP /w audio enabled and
users don't know how to disable it.
- all radeon users having switched their audio off
- most radeon users gave up on their DisplayPort or their radeon-based card
altogether (perhaps switching brand in the process, frustration kicking in)
- it's a recent regression and I've been lucky to catch it before the kernel
goes mainstream in major distros.

I'll still provide a dmesg dump, this time with drm.debug=0x06 (0x06 any good?
any prefered value?) by rebooting with audio back on and image gone.

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