Re: [Intel-gfx] [PATCH 2/9] drm/display/dp_mst: Handle old/new payload states in drm_dp_remove_payload()

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

On Thu, Jan 26, 2023 at 08:33:42PM +0200, Ville Syrjälä wrote:
> On Thu, Jan 26, 2023 at 07:37:04PM +0200, Ville Syrjälä wrote:
> > On Wed, Jan 25, 2023 at 01:48:45PM +0200, Imre Deak wrote:
> > > Atm, drm_dp_remove_payload() uses the same payload state to both get the
> > > vc_start_slot required for the payload removal DPCD message and to
> > > deduct time_slots from vc_start_slot of all payloads after the one being
> > > removed.
> > > 
> > > The above isn't always correct, as vc_start_slot must be the up-to-date
> > > version contained in the new payload state,
> > 
> > Why is that? In fact couldn't we just clear both start_slot and
> > pbn to 0 here?

The DP spec requires sending the actual start slot, even though the hubs
I checked ignored it and deleted all the allocation of the given VCPI
whatever start slot was used. Imo we should still not depend on this.

> OK, so it has to be the "current" start slot. Which in this case
> means new_payload since that's what's housed in the new topolpogy state
> which is the one getting mutated when streams are being removed/added.

Yes.

> Confusing, but seems correct
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> > 
> > > but time_slots must be the
> > > one used when the payload was previously added, contained in the old
> > > payload state. The new payload's time_slots can change vs. the old one
> > > if the current atomic commit changes the corresponding mode.
> > > 
> > > This patch let's drivers pass the old and new payload states to
> > > drm_dp_remove_payload(), but keeps these the same for now in all drivers
> > > not to change the behavior. A follow-up i915 patch will pass in that
> > > driver the correct old and new states to the function.
> > > 
> > > Cc: Lyude Paul <lyude@redhat.com>
> > > Cc: Ben Skeggs <bskeggs@redhat.com>
> > > Cc: Karol Herbst <kherbst@redhat.com>
> > > Cc: Harry Wentland <harry.wentland@amd.com>
> > > Cc: Alex Deucher <alexander.deucher@amd.com>
> > > Cc: Wayne Lin <Wayne.Lin@amd.com>
> > > Cc: stable@vger.kernel.org # 6.1
> > > Cc: dri-devel@lists.freedesktop.org
> > > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > > ---
> > >  .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c |  2 +-
> > >  drivers/gpu/drm/display/drm_dp_mst_topology.c | 22 ++++++++++---------
> > >  drivers/gpu/drm/i915/display/intel_dp_mst.c   |  4 +++-
> > >  drivers/gpu/drm/nouveau/dispnv50/disp.c       |  2 +-
> > >  include/drm/display/drm_dp_mst_helper.h       |  3 ++-
> > >  5 files changed, 19 insertions(+), 14 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> > > index 6994c9a1ed858..fed4ce6821161 100644
> > > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> > > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> > > @@ -179,7 +179,7 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
> > >  	if (enable)
> > >  		drm_dp_add_payload_part1(mst_mgr, mst_state, payload);
> > >  	else
> > > -		drm_dp_remove_payload(mst_mgr, mst_state, payload);
> > > +		drm_dp_remove_payload(mst_mgr, mst_state, payload, payload);
> > >  
> > >  	/* mst_mgr->->payloads are VC payload notify MST branch using DPCD or
> > >  	 * AUX message. The sequence is slot 1-63 allocated sequence for each
> > > diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > > index 5861b0a6247bc..ebf6e31e156e0 100644
> > > --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > > +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > > @@ -3342,7 +3342,8 @@ EXPORT_SYMBOL(drm_dp_add_payload_part1);
> > >   * drm_dp_remove_payload() - Remove an MST payload
> > >   * @mgr: Manager to use.
> > >   * @mst_state: The MST atomic state
> > > - * @payload: The payload to write
> > > + * @old_payload: The payload with its old state
> > > + * @new_payload: The payload to write
> > >   *
> > >   * Removes a payload from an MST topology if it was successfully assigned a start slot. Also updates
> > >   * the starting time slots of all other payloads which would have been shifted towards the start of
> > > @@ -3350,33 +3351,34 @@ EXPORT_SYMBOL(drm_dp_add_payload_part1);
> > >   */
> > >  void drm_dp_remove_payload(struct drm_dp_mst_topology_mgr *mgr,
> > >  			   struct drm_dp_mst_topology_state *mst_state,
> > > -			   struct drm_dp_mst_atomic_payload *payload)
> > > +			   const struct drm_dp_mst_atomic_payload *old_payload,
> > > +			   struct drm_dp_mst_atomic_payload *new_payload)
> > >  {
> > >  	struct drm_dp_mst_atomic_payload *pos;
> > >  	bool send_remove = false;
> > >  
> > >  	/* We failed to make the payload, so nothing to do */
> > > -	if (payload->vc_start_slot == -1)
> > > +	if (new_payload->vc_start_slot == -1)
> > >  		return;
> > 
> > So I take it the only reason we even have that is the copy being done in
> > drm_dp_mst_atomic_wait_for_dependencies()? I don't really understand
> > why any of that is being done tbh. If the new payload hasn't been
> > allocated yet then why can't its vc_start_slots just stay at -1
> > until that time?
> > 
> > This whole thing feels a bit weird since the payload table really isn't
> > your normal atomic state that is computed ahead of time. Instead it just
> > gets built up on as we go during the actual commit. So not really sure
> > why we're even tracking it in atomic state...
> > 
> > >  
> > >  	mutex_lock(&mgr->lock);
> > > -	send_remove = drm_dp_mst_port_downstream_of_branch(payload->port, mgr->mst_primary);
> > > +	send_remove = drm_dp_mst_port_downstream_of_branch(new_payload->port, mgr->mst_primary);
> > >  	mutex_unlock(&mgr->lock);
> > >  
> > >  	if (send_remove)
> > > -		drm_dp_destroy_payload_step1(mgr, mst_state, payload);
> > > +		drm_dp_destroy_payload_step1(mgr, mst_state, new_payload);
> > >  	else
> > >  		drm_dbg_kms(mgr->dev, "Payload for VCPI %d not in topology, not sending remove\n",
> > > -			    payload->vcpi);
> > > +			    new_payload->vcpi);
> > >  
> > >  	list_for_each_entry(pos, &mst_state->payloads, next) {
> > > -		if (pos != payload && pos->vc_start_slot > payload->vc_start_slot)
> > > -			pos->vc_start_slot -= payload->time_slots;
> > > +		if (pos != new_payload && pos->vc_start_slot > new_payload->vc_start_slot)
> > > +			pos->vc_start_slot -= old_payload->time_slots;
> > >  	}
> > > -	payload->vc_start_slot = -1;
> > > +	new_payload->vc_start_slot = -1;
> > >  
> > >  	mgr->payload_count--;
> > > -	mgr->next_start_slot -= payload->time_slots;
> > > +	mgr->next_start_slot -= old_payload->time_slots;
> > >  }
> > >  EXPORT_SYMBOL(drm_dp_remove_payload);
> > >  
> > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > > index ba29c294b7c1b..5f7bcb5c14847 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > > @@ -526,6 +526,8 @@ static void intel_mst_disable_dp(struct intel_atomic_state *state,
> > >  		to_intel_connector(old_conn_state->connector);
> > >  	struct drm_dp_mst_topology_state *mst_state =
> > >  		drm_atomic_get_mst_topology_state(&state->base, &intel_dp->mst_mgr);
> > > +	struct drm_dp_mst_atomic_payload *payload =
> > > +		drm_atomic_get_mst_payload_state(mst_state, connector->port);
> > >  	struct drm_i915_private *i915 = to_i915(connector->base.dev);
> > >  
> > >  	drm_dbg_kms(&i915->drm, "active links %d\n",
> > > @@ -534,7 +536,7 @@ static void intel_mst_disable_dp(struct intel_atomic_state *state,
> > >  	intel_hdcp_disable(intel_mst->connector);
> > >  
> > >  	drm_dp_remove_payload(&intel_dp->mst_mgr, mst_state,
> > > -			      drm_atomic_get_mst_payload_state(mst_state, connector->port));
> > > +			      payload, payload);
> > >  
> > >  	intel_audio_codec_disable(encoder, old_crtc_state, old_conn_state);
> > >  }
> > > diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> > > index edcb2529b4025..ed9d374147b8d 100644
> > > --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> > > +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> > > @@ -885,7 +885,7 @@ nv50_msto_prepare(struct drm_atomic_state *state,
> > >  
> > >  	// TODO: Figure out if we want to do a better job of handling VCPI allocation failures here?
> > >  	if (msto->disabled) {
> > > -		drm_dp_remove_payload(mgr, mst_state, payload);
> > > +		drm_dp_remove_payload(mgr, mst_state, payload, payload);
> > >  
> > >  		nvif_outp_dp_mst_vcpi(&mstm->outp->outp, msto->head->base.index, 0, 0, 0, 0);
> > >  	} else {
> > > diff --git a/include/drm/display/drm_dp_mst_helper.h b/include/drm/display/drm_dp_mst_helper.h
> > > index 41fd8352ab656..f5eb9aa152b14 100644
> > > --- a/include/drm/display/drm_dp_mst_helper.h
> > > +++ b/include/drm/display/drm_dp_mst_helper.h
> > > @@ -841,7 +841,8 @@ int drm_dp_add_payload_part2(struct drm_dp_mst_topology_mgr *mgr,
> > >  			     struct drm_dp_mst_atomic_payload *payload);
> > >  void drm_dp_remove_payload(struct drm_dp_mst_topology_mgr *mgr,
> > >  			   struct drm_dp_mst_topology_state *mst_state,
> > > -			   struct drm_dp_mst_atomic_payload *payload);
> > > +			   const struct drm_dp_mst_atomic_payload *old_payload,
> > > +			   struct drm_dp_mst_atomic_payload *new_payload);
> > >  
> > >  int drm_dp_check_act_status(struct drm_dp_mst_topology_mgr *mgr);
> > >  
> > > -- 
> > > 2.37.1
> > 
> > -- 
> > Ville Syrjälä
> > Intel
> 
> -- 
> Ville Syrjälä
> Intel