[Intel-gfx] [PATCH] drm/i915: Don't register CRT connector when it's fused off

[Ville Syrjälä]

On Mon, Nov 23, 2015 at 05:07:29PM +0200, Ville Syrjälä wrote:
> On Sat, Nov 21, 2015 at 10:44:12AM +0000, Chris Wilson wrote:
> > On Fri, Nov 20, 2015 at 10:35:41PM +0200, ville.syrjala at linux.intel.com wrote:
> > > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > 
> > > On some machines the CRT connector may be fused off. The weird thing
> > > about this setup is that the ADPA register works otherwise normally,
> > > except the enable bit is hardwired to 0. No one knows of any fuse
> > > register that would tell us if this is the case, so the only thing we
> > > can do (apart from a blacklist) is to try and set the enable bit and see
> > > if it sticks. If not, we don't register the connector at all. Obviously
> > > if the bit is already set when loading the driver we can just assume it
> > > works.
> > > 
> > > I've smoke tested this approach on several machines (GMCH and PCH),
> > > some with actual CRT connectors, some with shadow connectors, and
> > > obviously the machine (IVB) with the fused off connector. So far
> > > I've not seen any ill effects from this probe.
> > > 
> > > The main benefit is that we can actually run igt on machines with
> > > fused off connectors, without totally upsetting the state checker.
> > > 
> > > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > If we can't enable the VGA port, there's not much we can do with it.
> > 
> > Acked-by: Chris Wilson <chris at chris-wilson.co.uk>
> > 
> > I'm just a bit hesistant, in case there are machine out there that
> > simply do not report the hw state back (doubtful) or there are people
> > who make use of the false VGA as a fake output (like me, or perhaps
> > kvm-over-ip). I'll survive, I just use a fake HDMI output if there is no
> > VGA.
> 
> Based on my experience most machines that lack the physical connector
> still have a fully working ADPA register. I have two such machines
> myself. There's just this one machine at our office where it's
> totally fused off, and running igt on it is no fun unless we get rid
> of the connector.

Patch merged, thanks for the ack.

-- 
Ville Syrjälä
Intel OTC