drm/amd/display: Fix ISM dc_lock deadlock during suspend

[Why]
System hang observed during suspend/resume while video is playing.
amdgpu_dm_ism_disable() is called under dc_lock and waits for ISM
delayed work via disable_delayed_work_sync(). The work handlers
themselves take dc_lock, producing an ABBA deadlock when a worker is
in flight at suspend time.

[How]
Split the disable path into two phases with opposite locking
contracts:
  1. amdgpu_dm_ism_disable() -- quiesces workers, must NOT hold
     dc_lock.
  2. amdgpu_dm_ism_force_full_power() (new) -- drives the ISM FSM
     back to FULL_POWER_RUNNING, must hold dc_lock.

Reviewed-by: Sun peng (Leo) Li <sunpeng.li@amd.com>
Signed-off-by: Ray Wu <ray.wu@amd.com>
Signed-off-by: Ivan Lipski <ivan.lipski@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

3 files changed, 70 insertions, 12 deletions

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 3ae2f330c6b4..ba7f98a87808 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -2330,9 +2330,16 @@ static void amdgpu_dm_fini(struct amdgpu_device *adev)
 		adev->dm.idle_workqueue = NULL;
 	}
 
-	/* Disable ISM before dc_destroy() invalidates dm->dc */
+	/*
+	 * Disable ISM before dc_destroy() invalidates dm->dc.
+	 *
+	 * Quiesce workers first without dc_lock (they take dc_lock
+	 * themselves, so syncing under it would deadlock), then drive the
+	 * FSM back to FULL_POWER_RUNNING under dc_lock.
+	 */
+	amdgpu_dm_ism_disable(&adev->dm);
 	scoped_guard(mutex, &adev->dm.dc_lock)
-		amdgpu_dm_ism_disable(&adev->dm);
+		amdgpu_dm_ism_force_full_power(&adev->dm);
 
 	amdgpu_dm_destroy_drm_device(&adev->dm);
 
@@ -3364,9 +3371,14 @@ static int dm_suspend(struct amdgpu_ip_block *ip_block)
 	if (amdgpu_in_reset(adev)) {
 		enum dc_status res;
 
+		/* Quiesce ISM workers before taking dc_lock (workers take
+		 * dc_lock themselves; syncing under it would deadlock).
+		 */
+		amdgpu_dm_ism_disable(dm);
+
 		mutex_lock(&dm->dc_lock);
 
-		amdgpu_dm_ism_disable(dm);
+		amdgpu_dm_ism_force_full_power(dm);
 		dc_allow_idle_optimizations(adev->dm.dc, false);
 
 		dm->cached_dc_state = dc_state_create_copy(dm->dc->current_state);
@@ -3400,8 +3412,13 @@ static int dm_suspend(struct amdgpu_ip_block *ip_block)
 
 	amdgpu_dm_irq_suspend(adev);
 
+	/*
+	 * Quiesce ISM workers before taking dc_lock (workers take dc_lock
+	 * themselves; syncing under it would deadlock).
+	 */
+	amdgpu_dm_ism_disable(dm);
 	scoped_guard(mutex, &dm->dc_lock)
-		amdgpu_dm_ism_disable(dm);
+		amdgpu_dm_ism_force_full_power(dm);
 
 	hpd_rx_irq_work_suspend(dm);
 
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_ism.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_ism.c
index d03ea3bafd46..73eda7273a7b 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_ism.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_ism.c
@@ -516,13 +516,20 @@ static void dm_ism_sso_delayed_work_func(struct work_struct *work)
 }
 
 /**
- * amdgpu_dm_ism_disable - Disable the ISM
+ * amdgpu_dm_ism_disable - Quiesce ISM workers
  *
  * @dm: The amdgpu display manager
  *
- * Disable the idle state manager by disabling any ISM work, canceling pending
- * work, and waiting for in-progress work to finish. After disabling, the system
- * is left in DM_ISM_STATE_FULL_POWER_RUNNING state.
+ * Cancels and disables any pending or in-flight ISM delayed work and waits
+ * for in-progress work to finish. After this returns, no ISM worker can run
+ * and subsequent mod_delayed_work() calls become no-ops via
+ * clear_pending_if_disabled().
+ *
+ * Must NOT be called with dc_lock held: the workers themselves take dc_lock,
+ * so a synchronous wait under dc_lock would deadlock.
+ *
+ * The caller is responsible for driving the FSM back to FULL_POWER_RUNNING
+ * (under dc_lock) by calling amdgpu_dm_ism_force_full_power().
  */
 void amdgpu_dm_ism_disable(struct amdgpu_display_manager *dm)
 {
@@ -530,21 +537,54 @@ void amdgpu_dm_ism_disable(struct amdgpu_display_manager *dm)
 	struct amdgpu_crtc *acrtc;
 	struct amdgpu_dm_ism *ism;
 
-	ASSERT(mutex_is_locked(&dm->dc_lock));
+	/*
+	 * Caller must NOT hold dc_lock: the ISM delayed work handlers
+	 * acquire dc_lock themselves, so waiting for them via
+	 * disable_delayed_work_sync() while holding dc_lock would
+	 * self-deadlock against an in-flight worker.
+	 */
+	lockdep_assert_not_held(&dm->dc_lock);
 
 	drm_for_each_crtc(crtc, dm->ddev) {
 		acrtc = to_amdgpu_crtc(crtc);
 		ism = &acrtc->ism;
 
-		/* Cancel and disable any pending work */
 		disable_delayed_work_sync(&ism->delayed_work);
 		disable_delayed_work_sync(&ism->sso_delayed_work);
+	}
+}
+
+/**
+ * amdgpu_dm_ism_force_full_power - Force every CRTC's ISM FSM to FULL_POWER
+ *
+ * @dm: The amdgpu display manager
+ *
+ * Sends DM_ISM_EVENT_EXIT_IDLE_REQUESTED to every CRTC's ISM, leaving each
+ * FSM in FULL_POWER_RUNNING. Intended to be paired with
+ * amdgpu_dm_ism_disable(): callers should first quiesce workers (without
+ * dc_lock), then take dc_lock and call this helper.
+ *
+ * Must be called with dc_lock held.
+ */
+void amdgpu_dm_ism_force_full_power(struct amdgpu_display_manager *dm)
+{
+	struct drm_crtc *crtc;
+	struct amdgpu_crtc *acrtc;
+
+	/*
+	 * Caller must hold dc_lock: commit_event() drives the FSM and
+	 * may touch dc state via dc_allow_idle_optimizations() etc.
+	 */
+	lockdep_assert_held(&dm->dc_lock);
+
+	drm_for_each_crtc(crtc, dm->ddev) {
+		acrtc = to_amdgpu_crtc(crtc);
 
 		/*
 		 * When disabled, leave in FULL_POWER_RUNNING state.
-		 * EXIT_IDLE will not queue any work
+		 * EXIT_IDLE will not queue any work.
 		 */
-		amdgpu_dm_ism_commit_event(ism,
+		amdgpu_dm_ism_commit_event(&acrtc->ism,
 					   DM_ISM_EVENT_EXIT_IDLE_REQUESTED);
 	}
 }
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_ism.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_ism.h
index fde0ddc8d4e4..964408cd9a83 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_ism.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_ism.h
@@ -146,6 +146,7 @@ void amdgpu_dm_ism_fini(struct amdgpu_dm_ism *ism);
 void amdgpu_dm_ism_commit_event(struct amdgpu_dm_ism *ism,
 				enum amdgpu_dm_ism_event event);
 void amdgpu_dm_ism_disable(struct amdgpu_display_manager *dm);
+void amdgpu_dm_ism_force_full_power(struct amdgpu_display_manager *dm);
 void amdgpu_dm_ism_enable(struct amdgpu_display_manager *dm);
 
 #endif