[PATCH] radeon: add option so DVI always respect HPD over DDC

[Dave Airlie]

On Mon, 9 Sep 2019 at 08:52, Deucher, Alexander
<Alexander.Deucher at amd.com> wrote:
>
> > -----Original Message-----
> > From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of
> > Dave Airlie
> > Sent: Sunday, September 1, 2019 11:09 PM
> > To: amd-gfx at lists.freedesktop.org
> > Subject: [PATCH] radeon: add option so DVI always respect HPD over DDC
> >
> > From: Dave Airlie <airlied at redhat.com>
> >
> > Purelink FX-D120 (DVI over fibre extendeders) drive the HPD line low on the
> > GPU side when the monitor side device is unplugged or loses the connection.
> > However the GPU side device seems to cache EDID in this case. Per DVI spec
> > the HPD line must be driven in order for EDID to be done, but we've met
> > enough broken devices (mainly
> > VGA->DVI convertors) that do the wrong thing with HPD that we ignore
> > it if a DDC probe succeeds.
> >
> > This patch adds an option to the radeon driver to always respect HPD on DVI
> > connectors such that if the HPD line isn't driven then EDID isn't probed.
>
> Probably cleaner to make this a connector property rather than a global enable, but I'm not too pressed either way.

Just wanted a way to let them set it on the command line, rather than
run a script at bootup, but maybe it's cleaner, will look into it a
bit more.

Dave.