[Nouveau] NVAC "No Signal"

[Pierre Moreau]

On 01:15 am - Oct 21 2016, Lukas Wunner wrote:
> On Thu, Oct 20, 2016 at 10:08:28AM +0200, Lukas Wunner wrote:
> > On Wed, Oct 19, 2016 at 07:58:06PM +0200, Pierre Moreau wrote:
> > > For example, my laptop (which also has an NVAC) has been triggering the
> > > no-signal message on external monitors way before Ben???s patch landed,
> > > but only for some adapters. I haven???t tried Ben???s patch yet, nor
> > > yours, but I will certainly do it, and see what effect each of them has.
> > 
> > The external DP port on your MBP5,3 is switchable between GPUs and
> > the apple-gmux driver switches it in unison with the panel.  Thus
> > the NVAC cannot drive external displays when gmux is switched to
> > the MCP79.  (You probably were aware of this, just wanted to mention
>       ^^^^^
> I meant G96, sorry I mixed it up.
> 
> Lukas

Yes, that bit had stayed in my memory, that switching between the two GPUs
would not only switch them for the laptop screen, but for the external ones as
well. IIRC, I am getting the no signal in both cases, but I need to retest.

Pierre

> 
> > it in case you weren't.)  (In theory we could change vga_switcheroo
> > and apple-gmux to support switching the panel and the external port
> > separately rather than in unison if there is demand.  It's only
> > supported on MBPs introduced from 2008 to 2010 though, the 2011+
> > models can only drive external ports with the discrete GPU.)
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