Commen=
t # 6
on bug 10553=
4
from Ville Syrjala
(In reply to Alex Deucher from comment #5)
> (In reply to Christian K=C3=B6nig from comment #3)
> > What you can use is either an active DP to dual DVI converter (pr=
obably
> > rather expensive if such a thing even exists) or native DP/HDMI (=
if the
> > monitor has connectors for that).
>=20
> They are actually relatively common for just these sorts of scenarios.=
Not
> sure about cost however.
>=20
> (In reply to philipmorant from comment #4)
> > Thanks for replies. My monitor is DVI DL only.
> >=20
> > My old Haswell i5 4670 with HD4600 graphics was also single link =
DVI only
> > (https://c=
ommunities.intel.com/thread/44135), and it worked at 60Hz. Could
> > somebody please explain why haswell can do it but raven can't ?
>=20
> I'm not sure how the intel hw is designed. I can't comment on exactly=
what
> is happening. I suspect what is happening is that the intel driver is=
not
> validating the link requirements and treating the DVI port like HDMI a=
nd
> sending the high bandwidth mode over a single TMDS link. The monitor =
just
> happens to accept it.
FYI in i915 we validate everything when enumerating the modes, but during a
modeset we allow the user mode to exceed the DP++ dongle and sink limitatio=
ns
for just these sort of cases (source limitations we enforce always). The us=
er
has manually added the out-of-spec mode so presumably they know what they're
doing...
Also we can't reliably tell what kind of connector is present on the board =
so
we treat DVI and HDMI the same. DP++ we treat a little special because we c=
an't
actually read out the state of the CONFIG1 pin so we can't tell whether a t=
ype1
DVI DP++ dongle is present or not. So if we can't read out the dongle regis=
ters
and the connector *looks* like a DP++ in the video BIOS tables we assume the
dongle to be present. But again the user can still override this by forcing=
an
out-of-spec mode.