On Mon, 22 Jan 2018, Imre Deak <imre.deak@xxxxxxxxx> wrote:
> On Fri, Jan 19, 2018 at 05:45:16PM +0200, Imre Deak wrote:
>> On Thu, Oct 12, 2017 at 12:13:38PM -0700, Manasi Navare wrote:
>> > In case of eDP because the panel has a fixed mode, the link rate
>> > and lane count at which it is trained corresponds to the link BW
>> > required to support the native resolution of the panel. In case of
>> > panles with lower resolutions where fewer lanes are hooked up internally,
>> > that number is reflected in the MAX_LANE_COUNT DPCD register of the panel.
>> > So it is pointless to fallback to lower link rate/lane count in case
>> > of link training failure on eDP connector since the lower link BW
>> > will not support the native resolution of the panel and we cannot
>> > prune the preferred mode on the eDP connector.
>> >
>> > In case of Link training failure on the eDP panel, something is wrong
>> > in the HW internally and hence driver errors out with a loud
>> > and clear DRM_ERROR message.
>> >
>> > v2:
>> > * Fix the DEBUG_ERROR and add {} in else (Ville Syrjala)
>> >
>> > Cc: Clinton Taylor <clinton.a.taylor@xxxxxxxxx>
>> > Cc: Jim Bride <jim.bride@xxxxxxxxxxxxxxx>
>> > Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
>> > Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
>> > Cc: Dave Airlie <airlied@xxxxxxxxxx>
>> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
>> > Signed-off-by: Manasi Navare <manasi.d.navare@xxxxxxxxx>
>> > Reviewed-by: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
>>
>> This fell through the cracks, looks like it partially fixes
>> https://bugs.freedesktop.org/show_bug.cgi?id=103369
>>
>> Why link training fails there is not clear.
>
> Ok, the link training fail turned out to be a race between a modeset
> link training and a link retraining called from
> runtime_resume->intel_hpd_init->dp_detect. As Ville pointed out that
> one was fixed meanwhile by
>
> commit 42e5e65765265485ecf2a480c244d76c2c624449
> Author: Daniel Vetter <daniel.vetter@xxxxxxxx>
> AuthorDate: Mon Nov 13 17:01:40 2017 +0100
> Commit: Daniel Vetter <daniel.vetter@xxxxxxxx>
> CommitDate: Thu Nov 23 14:59:07 2017 +0100
>
> drm/i915: sync dp link status checks against atomic commmits
>
> I merged now this fix to address the other issue, adding the above bug
> as reference. Thanks for the patch and the review.
Thanks for the follow-up... but should we have added a Fixes: or cc:
stable tag here?
BR,
Jani.
>
> --Imre
>
>>
>> > ---
>> > drivers/gpu/drm/i915/intel_dp_link_training.c | 26 +++++++++++++++++---------
>> > 1 file changed, 17 insertions(+), 9 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
>> > index 05907fa..cf8fef8 100644
>> > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
>> > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
>> > @@ -328,14 +328,22 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
>> > return;
>> >
>> > failure_handling:
>> > - DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
>> > - intel_connector->base.base.id,
>> > - intel_connector->base.name,
>> > - intel_dp->link_rate, intel_dp->lane_count);
>> > - if (!intel_dp_get_link_train_fallback_values(intel_dp,
>> > - intel_dp->link_rate,
>> > - intel_dp->lane_count))
>> > - /* Schedule a Hotplug Uevent to userspace to start modeset */
>> > - schedule_work(&intel_connector->modeset_retry_work);
>> > + /* Dont fallback and prune modes if its eDP */
>> > + if (!intel_dp_is_edp(intel_dp)) {
>> > + DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
>> > + intel_connector->base.base.id,
>> > + intel_connector->base.name,
>> > + intel_dp->link_rate, intel_dp->lane_count);
>> > + if (!intel_dp_get_link_train_fallback_values(intel_dp,
>> > + intel_dp->link_rate,
>> > + intel_dp->lane_count))
>> > + /* Schedule a Hotplug Uevent to userspace to start modeset */
>> > + schedule_work(&intel_connector->modeset_retry_work);
>> > + } else {
>> > + DRM_ERROR("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
>> > + intel_connector->base.base.id,
>> > + intel_connector->base.name,
>> > + intel_dp->link_rate, intel_dp->lane_count);
>> > + }
>> > return;
>> > }
>> > --
>> > 2.1.4
>> >
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--
Jani Nikula, Intel Open Source Technology Center
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