Switchable graphics and radeon PX runtime

[Takashi Iwai]

At Fri, 14 Nov 2014 19:33:00 +1000,
Dave Airlie wrote:
> 
> On 14 November 2014 18:12, Takashi Iwai <tiwai at suse.de> wrote:
> > Hi Alex,
> >
> > we've got a few bug reports about the behavior of radeon driver on
> > machines with Intel+AMD "switchable graphics" (no Muxless).  So far,
> > it seems that the sane only way to make the machine working is to get
> > back to the old vgaswitcheroo behavior via radeon.runpm=0.  Without
> > it, radeon GPU gives a spurious output as connected, eventually
> > crashes GNOME.  (Also, from the nature of the switchable graphics,
> > vgaswitcheroo looks more intuitive to me.)
> 
> vgaswitcheroo only matters if there is a MUX, the point of it is to drive
> the MUX.
> 
> dynamic poweroff makes more sense, switcheroo on/off switch was
> just a hack.

Well, I find the current form fairly unintuitive, at least, for the
switchable (not optimus) graphics.
With dynamic PM, the card is activated on demand.  So you may enable
outputs of both cards at any time, right?

Currently, all outputs from both cards are exposed in Xrandr,
e.g. LVDS1 DP1, HDMI1, VGA1, LVDS-1-1, HDMI-1-2, DisplayPort-1-2, and
VGA-1-1.  How can user-space know which one should be activated and
which not, when you can use effectively only a single card?

> > How are such machines supposed to work with the recent system?  Is PX
> > wrongly detected on them, or something else missing?
> 
> It sounds like the connector is wrongly detected and that should be what
> is fixed.

Yeah, that's a problem indeed.  In the bug report, both LVDS1 and
LVDS-1-1 are reported to be connected at the same time while the
latter doesn't get any real size and position.  We didn't trace
whether this is the culprit of crash of GNOME, but at least, it looks
fairly weird.

I forgot to give the original bug report:
  http://bugzilla.opensuse.org/show_bug.cgi?id=904417

and the xrandr output is found at
  http://bugzilla.opensuse.org/show_bug.cgi?id=904417#c18


thanks,

Takashi