[Intel-gfx] [PATCH] drm/i915: tune down the fast link training vs boot fail

[Daniel Vetter]

On Wed, Dec 14, 2016 at 04:56:33PM +0200, Jani Nikula wrote:
> On Wed, 14 Dec 2016, Daniel Vetter <daniel at ffwll.ch> wrote:
> > On Tue, Dec 13, 2016 at 10:23:05PM +0200, Ville Syrjälä wrote:
> >> On Tue, Dec 13, 2016 at 08:54:14PM +0100, Daniel Vetter wrote:
> >> > It's been unfixed since a while and no one is immediately working on
> >> > this. And we have the FIXME already. And now also a task in the DP
> >> > team's backlog.
> >> > 
> >> > Cc: Linus Torvalds <torvalds at linux-foundation.org>
> >> > Cc: stable at vger.kernel.org
> >> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> >> > References: https://lists.freedesktop.org/archives/intel-gfx/2016-July/101951.html
> >> > Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> >> > ---
> >> > Hi Linus,
> >> > 
> >> > Feel free to apply directly in case it annoys too much and you don't
> >> > want to wait for your presents ;-)
> >> > 
> >> > Cheers, Daniel
> >> > ---
> >> >  drivers/gpu/drm/i915/intel_dp.c | 4 ++--
> >> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >> > 
> >> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> >> > index db75bb924e48..6e875d42642a 100644
> >> > --- a/drivers/gpu/drm/i915/intel_dp.c
> >> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> >> > @@ -4014,8 +4014,8 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
> >> >  		return;
> >> >  
> >> >  	/* FIXME: we need to synchronize this sort of stuff with hardware
> >> > -	 * readout */
> >> > -	if (WARN_ON_ONCE(!intel_dp->lane_count))
> >> > +	 * readout. Currently fast link training doesn't work on boot-up. */
> >> 
> >> s/fast link training/link retraining/ is what I'd put there.
> >
> > Adjusted ...
> >> 
> >> I'm a bit sad to hide it but doesn't look like the proper solution is
> >> going to happen any time soon.
> >> 
> >> Acked-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> >
> > ... and merged since CI seems to approve too ;-)
> 
> *sigh* you could've added debug logging at least. Now it's pretty much
> guaranteed nobody will look at this. It's not right to end up here
> without link params. :(

I've made a JIRA internally to fix this and assigned it to Paul Parenteau
for handling with his DP folks. But I'm happy to also r-b stamp a patch
that adds some debug output here if you want that too. At least I thought
the problem is fairly well-understood, so didn't think this was needed.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch