On Thu, Oct 02, 2014 at 10:00:50AM +0200, Daniel Vetter wrote: > On Thu, Oct 02, 2014 at 01:30:48PM +1000, Dave Airlie wrote: > > Hey guys, > > > > so I have a haswell ULT laptop (lenovo t440s), and got access to a > > Samsung single panel 4k monitor (no MST). > > > > Now we detect the monitor fine, but unfortunately the ULT hsw can't > > run it over DP, as it has clock limits in place. However we still > > offer the 60hz mode and we pick it by default, ensuing black screens. > > > > I've tested the same monitor with a haswell in a t540p and it works > > fine due to having the higher limits in place. > > We have the IS_HSW_ULX check in intel_dp_max_link_bw, and that's used by > both compute_config and mode_valid. So it should work, and from a quick > look I don't see any bugs. But obviously something is busted. Just to be a bit more specific: ULT != ULX, the two SKUs have different limits. The test in intel_dp_max_link_bw() is about eDP/DP max link rate: HBR2(ULT) Vs HBR(ULX). I'd go with Ville, that sounds like CDCLK is the limiting factor, and we're missing these checks. From a cursory glance, it doesn't seem we can do 4k on ULT. -- Damien _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
