On Tue, Dec 01, 2015 at 01:41:49PM +0000, Chris Wilson wrote:
> On Tue, Dec 01, 2015 at 03:08:34PM +0200, ville.syrjala@xxxxxxxxxxxxxxx wrote:
> > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> >
> > Unfortunatey there appear to quite a few HSW/BDW machines (eg.
> > NUCs, Brix Pro) in the wild with LPT/WPT-H but non-working FDI.
> > FDI training fails every single time on these machines. Dunno,
> > maybe they just didn't bother wiring it up or something?
> >
> > Unfortunately all the fuse bits and whatnot are telling us that
> > the CRT connector is present. And so what we get from this is tons
> > of false positives from the CI systems due to VGA connector forcing.
> >
> > I've not found any way to detect this purely from hardware, so we
> > have to resort to looking at the VBT int_crt_support bit. We used
> > to check this bit on all platforms, but that broke all the old
> > machines, so the check was then restricted to VLV only in
> > commit 84b4e042c470 ("drm/i915: only apply crt_present check on VLV")
> >
> > Considering HSW and VLV VBT probably got defined around the same time,
> > it should be reasonably safe to assume that the bits is sane for
> > HSW/BDW as well. At least I have one copy of some VBT spec here that
> > says it's meant for both VLV and HSW, and it knows about the bit
> > (lists it being valid from version 155 onwards). Also I have two
> > HSW desktop machines with actual CRT ports and both have
> > int_crt_support==1 in their VBTs.
> >
> > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/intel_display.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index e80387dd6582..29ea4c458ab3 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -14263,7 +14263,7 @@ static bool intel_crt_present(struct drm_device *dev)
> > if (HAS_DDI(dev) && I915_READ(DDI_BUF_CTL(PORT_A)) & DDI_A_4_LANES)
> > return false;
> >
> > - if (IS_VALLEYVIEW(dev) && !dev_priv->vbt.int_crt_support)
> > + if ((HAS_DDI(dev) || IS_VALLEYVIEW(dev)) && !dev_priv->vbt.int_crt_support)
>
> Would it not be better to move this knowledge to vbt if it is version
> dependent?
>
> vbt.int_crtc_support = (UNKNOWN, NOT_PRESENT, PRESENT)
>
> then
>
> if (dev_priv->vbt.int_crt_support == NOT_PRESENT)
> > return false;
I'm not sure the UNKNWON value really buys us anything. But I suppose we
could just do this:
general = find_section(bdb, BDB_GENERAL_FEATURES);
if (general) {
dev_priv->vbt.int_tv_support = general->int_tv_support;
- dev_priv->vbt.int_crt_support = general->int_crt_support;
+ if (HAS_DDI(dev_priv) || IS_VALLEYIEW(dev_priv))
+ dev_priv->vbt.int_crt_support = general->int_crt_support;
The other option is to make it check the version. But I'm not sure if
that's entirely safe. For extra paranoia I guess we could do both,
just in case there's some early VLV/HSW out there with <155 VBT
version.
--
Ville Syrjälä
Intel OTC
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