Re: [PATCH] drm/i915: vlv: fix DP PHY lockup due to invalid PP sequencer setup

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Jan 30, 2014 at 04:52:24PM +0100, Daniel Vetter wrote:
> On Thu, Jan 30, 2014 at 04:50:42PM +0200, Imre Deak wrote:
> > Atm we setup the HW panel power sequencer logic both for eDP and DP
> > ports. On eDP we then go on and start the power on sequence and commence
> > with link training when it's ready. On DP we don't do the power on
> > sequencing but do the link training immediately. At this point the DP
> > PHY block gets stuck, since - supposedly - it is waiting for the power
> > on sequence to finish. The actual register write that seems to hold off
> > the PHY is PIPEX_PP_ON_DELAYS[Panel Control Port Select]. Writing here
> > a non-0 value eventually sets PIPEX_PP_STATUS[Require Asset Status] to
> > 1 and blocks the PHY until the panel power on is ready.
> > 
> > Fix this by not doing any PP sequencing setup for DP ports.
> > 
> > Thanks to Ville Syrjälä, Jesse Barnes and Todd Previte for the help in
> > tracking this down.
> > 
> > Signed-off-by: Imre Deak <imre.deak@intel.com>
> 
> Ah, the infamous ABCD hack we're using all over the place in intel_lvds.c.
> On edp we didn't have a need for it thus far since the "require asset
> status" checks have all been fused of, with the PP being on the PCH and
> the edp port on the north display block. If this is really all we need to
> appease the hardware then I'm heavily in favour of it as opposed to
> resurrect the ABCD hack for intel_dp.c.
> 
> One thing though: Should we add a check for the "Required Asset Status"
> bit somewhere? I don't really have a good idea for a spot to put this
> into, hence the question.

Also: Picked up for -fixes, thanks for the patch.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch