drm/mst: Refactor the flow for payload allocation/removement

[Why]
Today, the allocation/deallocation steps and status is a bit unclear.

For instance, payload->vc_start_slot = -1 stands for "the failure of
updating DPCD payload ID table" and can also represent as "payload is not
allocated yet". These two cases should be handled differently and hence
better to distinguish them for better understanding.

[How]
Define enumeration - ALLOCATION_LOCAL, ALLOCATION_DFP and ALLOCATION_REMOTE
to distinguish different allocation status. Adjust the code to handle
different status accordingly for better understanding the sequence of
payload allocation and payload removement.

For payload creation, the procedure should look like this:
DRM part 1:
* step 1 - update sw mst mgr variables to add a new payload
* step 2 - add payload at immediate DFP DPCD payload table

Driver:
* Add new payload in HW and sync up with DFP by sending ACT

DRM Part 2:
* Send ALLOCATE_PAYLOAD sideband message to allocate bandwidth along the
  virtual channel.

And as for payload removement, the procedure should look like this:
DRM part 1:
* step 1 - Send ALLOCATE_PAYLOAD sideband message to release bandwidth
           along the virtual channel
* step 2 - Clear payload allocation at immediate DFP DPCD payload table

Driver:
* Remove the payload in HW and sync up with DFP by sending ACT

DRM part 2:
* update sw mst mgr variables to remove the payload

Note that it's fine to fail when communicate with the branch device
connected at immediate downstrean-facing port, but updating variables of
SW mst mgr and HW configuration should be conducted anyway. That's because
it's under commit_tail and we need to complete the HW programming.

Changes since v1:
* Remove the set but not use variable 'old_payload' in function
  'nv50_msto_prepare'. Catched by kernel test robot <lkp@intel.com>

Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230807025639.1612361-3-Wayne.Lin@amd.com

1 files changed, 11 insertions, 10 deletions

diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index d18e24b6f1eb..39e9ba4139c7 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -882,21 +882,26 @@ struct nouveau_encoder *nv50_real_outp(struct drm_encoder *encoder)
 
 static void
 nv50_msto_cleanup(struct drm_atomic_state *state,
-		  struct drm_dp_mst_topology_state *mst_state,
+		  struct drm_dp_mst_topology_state *new_mst_state,
 		  struct drm_dp_mst_topology_mgr *mgr,
 		  struct nv50_msto *msto)
 {
 	struct nouveau_drm *drm = nouveau_drm(msto->encoder.dev);
-	struct drm_dp_mst_atomic_payload *payload =
-		drm_atomic_get_mst_payload_state(mst_state, msto->mstc->port);
+	struct drm_dp_mst_atomic_payload *new_payload =
+		drm_atomic_get_mst_payload_state(new_mst_state, msto->mstc->port);
+	struct drm_dp_mst_topology_state *old_mst_state =
+		drm_atomic_get_old_mst_topology_state(state, mgr);
+	const struct drm_dp_mst_atomic_payload *old_payload =
+		drm_atomic_get_mst_payload_state(old_mst_state, msto->mstc->port);
 
 	NV_ATOMIC(drm, "%s: msto cleanup\n", msto->encoder.name);
 
 	if (msto->disabled) {
 		msto->mstc = NULL;
 		msto->disabled = false;
+		drm_dp_remove_payload_part2(mgr, new_mst_state, old_payload, new_payload);
 	} else if (msto->enabled) {
-		drm_dp_add_payload_part2(mgr, state, payload);
+		drm_dp_add_payload_part2(mgr, state, new_payload);
 		msto->enabled = false;
 	}
 }
@@ -910,19 +915,15 @@ nv50_msto_prepare(struct drm_atomic_state *state,
 	struct nouveau_drm *drm = nouveau_drm(msto->encoder.dev);
 	struct nv50_mstc *mstc = msto->mstc;
 	struct nv50_mstm *mstm = mstc->mstm;
-	struct drm_dp_mst_topology_state *old_mst_state;
-	struct drm_dp_mst_atomic_payload *payload, *old_payload;
+	struct drm_dp_mst_atomic_payload *payload;
 
 	NV_ATOMIC(drm, "%s: msto prepare\n", msto->encoder.name);
 
-	old_mst_state = drm_atomic_get_old_mst_topology_state(state, mgr);
-
 	payload = drm_atomic_get_mst_payload_state(mst_state, mstc->port);
-	old_payload = drm_atomic_get_mst_payload_state(old_mst_state, mstc->port);
 
 	// 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, old_payload, payload);
+		drm_dp_remove_payload_part1(mgr, mst_state, payload);
 
 		nvif_outp_dp_mst_vcpi(&mstm->outp->outp, msto->head->base.index, 0, 0, 0, 0);
 	} else {