Re: [PATCH 06/14] drm/i915/dp: Send only a single modeset-retry uevent for a commit

[Imre Deak <imre.deak@intel.com>]

On Wed, Jul 24, 2024 at 07:29:33AM +0300, Murthy, Arun R wrote:
> 
> > -----Original Message-----
> > From: Intel-gfx <intel-gfx-bounces@lists.freedesktop.org> On Behalf Of Imre
> > Deak
> > Sent: Monday, July 22, 2024 10:25 PM
> > To: intel-gfx@lists.freedesktop.org
> > Subject: [PATCH 06/14] drm/i915/dp: Send only a single modeset-retry uevent
> > for a commit
> >
> > There are multiple failure cases a modeset-retry uevent can be sent for a link
> > (TBT tunnel BW allocation failure, unrecoverable link training failure), a follow-
> > up patch adding the handling for a new case where the DP MST payload
> > allocation fails. The uevent is the same in all cases, sent to all the connectors on
> > the link, so in case of multiple failures there is no point in sending a separate
> > uevent for each failure; prevent this, sending only a single modeset-retry
> > uevent for a commit.
> >
> Is an exit condition required with some 'x' retry so that this retry
> doesn't end up in an infinite loop.  For link training failure the
> link rate/lane count is reduced and when it reaches the least can
> exit, but for BW allocation failures/payload failure this may not be
> the case.

This is an error condition the driver reports (asynchronously) if a
modeset request by userspace/client failed. It would be incorrect not to
report this error, leaving the output in a blank, enabled state.

I think that userspace/client should handle such failures - in the
above case a buggy sink - by disabling the output.

> Thanks and Regards,
> Arun R Murthy
> --------------------
> > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_display_types.h | 1 +
> >  drivers/gpu/drm/i915/display/intel_dp.c            | 6 ++++++
> >  2 files changed, 7 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h
> > b/drivers/gpu/drm/i915/display/intel_display_types.h
> > index a9d2acdc51a4a..3501125c55158 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> > +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> > @@ -1754,6 +1754,7 @@ struct intel_dp {
> >       u8 lane_count;
> >       u8 sink_count;
> >       bool link_trained;
> > +     bool needs_modeset_retry;
> >       bool use_max_params;
> >       u8 dpcd[DP_RECEIVER_CAP_SIZE];
> >       u8 psr_dpcd[EDP_PSR_RECEIVER_CAP_SIZE];
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> > b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 421e970b3c180..0882dddd97206 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -2876,6 +2876,11 @@ intel_dp_queue_modeset_retry_for_link(struct
> > intel_atomic_state *state,
> >       struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> >       int i;
> >
> > +     if (intel_dp->needs_modeset_retry)
> > +             return;
> > +
> > +     intel_dp->needs_modeset_retry = true;
> > +
> >       if (!intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DP_MST)) {
> >               intel_dp_queue_modeset_retry_work(intel_dp-
> > >attached_connector);
> >
> > @@ -3009,6 +3014,7 @@ void intel_dp_set_link_params(struct intel_dp
> > *intel_dp,  {
> >       memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
> >       intel_dp->link_trained = false;
> > +     intel_dp->needs_modeset_retry = false;
> >       intel_dp->link_rate = link_rate;
> >       intel_dp->lane_count = lane_count;
> >  }
> > --
> > 2.44.2
>