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

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 15 Dec 2016, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Wed, Dec 14, 2016 at 04:56:33PM +0200, Jani Nikula wrote:
>> On Wed, 14 Dec 2016, Daniel Vetter <daniel@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@linux-foundation.org>
>> >> > Cc: stable@vger.kernel.org
>> >> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> >> > References: https://lists.freedesktop.org/archives/intel-gfx/2016-July/101951.html
>> >> > Signed-off-by: Daniel Vetter <daniel.vetter@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@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.

Oh, okay. Then it's just that *I* didn't understand the problem well. :(

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center