From 6366fc70deb9aaf1db4a46916af14fa3c5a115ab Mon Sep 17 00:00:00 2001
From: Lyude Paul <lyude@redhat.com>
Date: Wed, 17 Aug 2022 15:38:44 -0400
Subject: [PATCH] drm/display/dp_mst: Maintain time slot allocations when deleting payloads
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Git-commit: 6366fc70deb9aaf1db4a46916af14fa3c5a115ab
Patch-mainline: v6.1-rc1
References: bsc#1206843

Currently, we set drm_dp_atomic_payload->time_slots to 0 in order to
indicate that we're about to delete a payload in the current atomic state.
Since we're going to be dropping all of the legacy code for handling the
payload table however, we need to be able to ensure that we still keep
track of the current time slot allocations for each payload so we can reuse
this info when asking the root MST hub to delete payloads. We'll also be
using it to recalculate the start slots of each VC.

So, let's keep track of the intent of a payload in drm_dp_atomic_payload by
adding ->delete, which we set whenever we're planning on deleting a payload
during the current atomic commit.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Wayne Lin <Wayne.Lin@amd.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Fangzhi Zuo <Jerry.Zuo@amd.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Sean Paul <sean@poorly.run>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220817193847.557945-16-lyude@redhat.com
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/display/drm_dp_mst_topology.c |   14 +++++++-------
 include/drm/display/drm_dp_mst_helper.h       |    7 ++++++-
 2 files changed, 13 insertions(+), 8 deletions(-)

--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -4410,7 +4410,7 @@ int drm_dp_atomic_find_time_slots(struct
 		 * releasing and allocating the same timeslot allocation,
 		 * which is an error
 		 */
-		if (WARN_ON(!prev_slots)) {
+		if (drm_WARN_ON(mgr->dev, payload->delete)) {
 			drm_err(mgr->dev,
 				"cannot allocate and release time slots on [MST PORT:%p] in the same state\n",
 				port);
@@ -4515,10 +4515,10 @@ int drm_dp_atomic_release_time_slots(str
 	}
 
 	drm_dbg_atomic(mgr->dev, "[MST PORT:%p] TU %d -> 0\n", port, payload->time_slots);
-	if (payload->time_slots) {
+	if (!payload->delete) {
 		drm_dp_mst_put_port_malloc(port);
-		payload->time_slots = 0;
 		payload->pbn = 0;
+		payload->delete = true;
 	}
 
 	return 0;
@@ -5242,7 +5242,7 @@ drm_dp_mst_duplicate_state(struct drm_pr
 
 	list_for_each_entry(pos, &old_state->payloads, next) {
 		/* Prune leftover freed timeslot allocations */
-		if (!pos->time_slots)
+		if (pos->delete)
 			continue;
 
 		payload = kmemdup(pos, sizeof(*payload), GFP_KERNEL);
@@ -5274,8 +5274,8 @@ static void drm_dp_mst_destroy_state(str
 	int i;
 
 	list_for_each_entry_safe(pos, tmp, &mst_state->payloads, next) {
-		/* We only keep references to ports with non-zero VCPIs */
-		if (pos->time_slots)
+		/* We only keep references to ports with active payloads */
+		if (!pos->delete)
 			drm_dp_mst_put_port_malloc(pos->port);
 		kfree(pos);
 	}
@@ -5403,7 +5403,7 @@ drm_dp_mst_atomic_check_payload_alloc_li
 
 	list_for_each_entry(payload, &mst_state->payloads, next) {
 		/* Releasing payloads is always OK-even if the port is gone */
-		if (!payload->time_slots) {
+		if (payload->delete) {
 			drm_dbg_atomic(mgr->dev, "[MST PORT:%p] releases all time slots\n",
 				       payload->port);
 			continue;
--- a/include/drm/display/drm_dp_mst_helper.h
+++ b/include/drm/display/drm_dp_mst_helper.h
@@ -555,7 +555,12 @@ struct drm_dp_mst_atomic_payload {
 	 */
 	int time_slots;
 	int pbn;
-	bool dsc_enabled;
+
+	/** @delete: Whether or not we intend to delete this payload during this atomic commit */
+	bool delete : 1;
+	/** @dsc_enabled: Whether or not this payload has DSC enabled */
+	bool dsc_enabled : 1;
+
 	struct list_head next;
 };