Re: [PATCH] drm/i915: Enable 5.4Ghz (HBR2) link rate for Displayport 1.2-capable devices

[Damien Lespiau <damien.lespiau@intel.com>]

On Fri, Jan 17, 2014 at 07:58:58AM -0700, Todd Previte wrote:
> >>diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> >>index 7df5085..f92d1c0 100644
> >>--- a/drivers/gpu/drm/i915/intel_dp.c
> >>+++ b/drivers/gpu/drm/i915/intel_dp.c
> >>@@ -102,7 +102,10 @@ intel_dp_max_link_bw(struct intel_dp *intel_dp)
> >>         case DP_LINK_BW_2_7:
> >>                 break;
> >>         case DP_LINK_BW_5_4: /* 1.2 capable displays may advertise higher bw */
> >>-               max_link_bw = DP_LINK_BW_2_7;
> >>+        if (intel_dp->dpcd[DP_DPCD_REV] == 0x12)
> >>+            max_link_bw = DP_LINK_BW_5_4;
> >>+        else
> >>+            max_link_bw = DP_LINK_BW_2_7;
> >Is this really required, i.e. do we have dp 1.1 machines in the wild
> >which advertise 5.4 but can't? In any case you also need to have a
> >IS_HSW || IS_BDW check here, since only those two platforms support
> >5.4 GHz.
> I've not seen a case where a 1.1a capable device advertises HBR2,
> no. I *have* seen the case where the sink reports that it only
> supports RBR (1.62Ghz) but is in fact capable of 2.7Ghz. This is
> more of a safety measure to eliminate potential training problems,
> but is not strictly necessary to support HBR2. It does need the
> IS_HSW || IS_BDW though, so I'll fix that and resend.

Can we make it IS_HSW || INTEL_INFO(dev)->gen >= 8, we can't quite
predict the future but new platforms supporting what old platforms do
support is a bet we take elsewere.

-- 
Damien