From 222416869a08ca4284f87823a938284ecfc7b297 Mon Sep 17 00:00:00 2001
From: Dom Cobley <popcornmix@gmail.com>
Date: Mon, 26 Jul 2021 18:02:11 +0100
Subject: [PATCH] Revert "drm/vc4: kms: Remove async modeset semaphore"

This reverts commit a28f2f0df6da70dec509b965635f0d5f71f9a9f7.
---
 drivers/gpu/drm/vc4/vc4_crtc.c | 13 +++++++++++++
 drivers/gpu/drm/vc4/vc4_drv.h  |  2 ++
 drivers/gpu/drm/vc4/vc4_kms.c  | 24 ++++++++++++++++++++++--
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index 0771fd9..008d264 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -766,6 +766,7 @@ vc4_async_page_flip_complete(struct vc4_seqno_cb *cb)
 		container_of(cb, struct vc4_async_flip_state, cb);
 	struct drm_crtc *crtc = flip_state->crtc;
 	struct drm_device *dev = crtc->dev;
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	struct drm_plane *plane = crtc->primary;
 
 	vc4_plane_async_set_fb(plane, flip_state->fb);
@@ -797,6 +798,8 @@ vc4_async_page_flip_complete(struct vc4_seqno_cb *cb)
 	}
 
 	kfree(flip_state);
+
+	up(&vc4->async_modeset);
 }
 
 /* Implements async (non-vblank-synced) page flips.
@@ -811,6 +814,7 @@ static int vc4_async_page_flip(struct drm_crtc *crtc,
 			       uint32_t flags)
 {
 	struct drm_device *dev = crtc->dev;
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	struct drm_plane *plane = crtc->primary;
 	int ret = 0;
 	struct vc4_async_flip_state *flip_state;
@@ -839,6 +843,15 @@ static int vc4_async_page_flip(struct drm_crtc *crtc,
 	flip_state->crtc = crtc;
 	flip_state->event = event;
 
+	/* Make sure all other async modesetes have landed. */
+	ret = down_interruptible(&vc4->async_modeset);
+	if (ret) {
+		drm_framebuffer_put(fb);
+		vc4_bo_dec_usecnt(bo);
+		kfree(flip_state);
+		return ret;
+	}
+
 	/* Save the current FB before it's replaced by the new one in
 	 * drm_atomic_set_fb_for_plane(). We'll need the old FB in
 	 * vc4_async_page_flip_complete() to decrement the BO usecnt and keep
diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
index 9d7e0ee..f73f0a6 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.h
+++ b/drivers/gpu/drm/vc4/vc4_drv.h
@@ -216,6 +216,8 @@ struct vc4_dev {
 		struct work_struct reset_work;
 	} hangcheck;
 
+	struct semaphore async_modeset;
+
 	struct drm_modeset_lock ctm_state_lock;
 	struct drm_private_obj ctm_manager;
 	struct drm_private_obj hvs_channels;
diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
index 24dea3a..7b02bff 100644
--- a/drivers/gpu/drm/vc4/vc4_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_kms.c
@@ -424,6 +424,8 @@ vc4_atomic_complete_commit(struct drm_atomic_state *state)
 		clk_request_done(core_req);
 
 	drm_atomic_state_put(state);
+
+	up(&vc4->async_modeset);
 }
 
 static void commit_work(struct work_struct *work)
@@ -481,17 +483,26 @@ static int vc4_atomic_commit(struct drm_device *dev,
 			     struct drm_atomic_state *state,
 			     bool nonblock)
 {
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	int ret;
 
 	if (state->async_update) {
-		ret = drm_atomic_helper_prepare_planes(dev, state);
+		ret = down_interruptible(&vc4->async_modeset);
 		if (ret)
 			return ret;
 
+		ret = drm_atomic_helper_prepare_planes(dev, state);
+		if (ret) {
+			up(&vc4->async_modeset);
+			return ret;
+		}
+
 		drm_atomic_helper_async_commit(dev, state);
 
 		drm_atomic_helper_cleanup_planes(dev, state);
 
+		up(&vc4->async_modeset);
+
 		return 0;
 	}
 
@@ -508,14 +519,21 @@ static int vc4_atomic_commit(struct drm_device *dev,
 
 	INIT_WORK(&state->commit_work, commit_work);
 
-	ret = drm_atomic_helper_prepare_planes(dev, state);
+	ret = down_interruptible(&vc4->async_modeset);
 	if (ret)
 		return ret;
 
+	ret = drm_atomic_helper_prepare_planes(dev, state);
+	if (ret) {
+		up(&vc4->async_modeset);
+		return ret;
+	}
+
 	if (!nonblock) {
 		ret = drm_atomic_helper_wait_for_fences(dev, state, true);
 		if (ret) {
 			drm_atomic_helper_cleanup_planes(dev, state);
+			up(&vc4->async_modeset);
 			return ret;
 		}
 	}
@@ -995,6 +1013,8 @@ int vc4_kms_load(struct drm_device *dev)
 		vc4->load_tracker_enabled = true;
 	}
 
+	sema_init(&vc4->async_modeset, 1);
+
 	/* Set support for vblank irq fast disable, before drm_vblank_init() */
 	dev->vblank_disable_immediate = true;
 
-- 
2.7.4