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

[Todd Previte <tprevite@gmail.com>]

On 1/17/2014 8:08 AM, Damien Lespiau wrote:
> 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.
>
Sounds like a better solution. I should have that integrated shortly.

-T