Re: [PATCH] drm/i915/crt: Do not rely upon the HPD presence pin

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Jun 08, 2012 at 11:23:10PM +0100, Chris Wilson wrote:
> On Sat, 9 Jun 2012 00:22:12 +0200, Daniel Vetter <daniel@ffwll.ch> wrote:
> > On Thu, May 31, 2012 at 01:08:53PM +0100, Chris Wilson wrote:
> > > Whilst most monitors do wire up the HPD presence pin, it seems quite a
> > > few KVM do not. Therefore if we simply rely on the HPD pin being
> > > asserted to indicate a connected monitor we fail miserable, so fall back
> > > to performing a DCC query for the EDID.
> > > 
> > > Reported-and-tested-by: Matthieu LAVIE <boiteamadmax@hotmail.com>
> > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=50501
> > > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > 
> > Ok, this blew up ... Can you please resend, with Dave's suggestion for a
> > rectified commit message & comment and with a check added such that we
> > don't try to do load_detect on HAS_HOTPLUG machines - I guess it doesn't
> > work too well.
> 
> I disagree, if we cannot trust the hw autodetection, then we know that
> there are monitors/kvm that do not report an EDID and so we need to do
> the whole shebang. Which will continue to annoy Linus since his machine
> is behaving as expected given the circumstances.

Well, I don't disagree on doing the whole shebang. The proplem is that the
load-detect code as-is is gen3 only (and maybe gen4, haven't checked
that) - it surely can't work on pch split platforms if half the registers
we use in there are gone.

Until that is fixed and properly tested on all relevant platforms, we
should be able to help the bug reporters by simply using the edid
detection, but bailing on the load detect stuff for all HAS_HOTPLUG
platforms (as we do now already). I'll whip up a patch.

For actual load-detect stuff is imo -next material, and I think we should
dodge that bullet until we have an actual bug reporter wanting it ...
-Daniel
-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48