[Nouveau] NVAC "No Signal"

[Lukas Wunner]

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
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.)

Best regards,

Lukas