[PATCH 1/7] drm/mediatek: fix atomic_state reference counting

[Bibby Hsieh <bibby.hsieh@mediatek.com>]

The DRM core takes care of all atomic state refcounting.
However, mediatek drm defers some work that accesses planes
and plane_states in drm_atomic_state, and must therefore
keep its own atomic state references until this work complete.

We take the atomic_state reference in atomic_fulsh() and ensure all the
information in atomic_state already was updated in hardware for
showing on screen and then schedules unreference_work to drop references
on atomic_state.

Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.")

Signed-off-by: Bibby Hsieh <bibby.hsieh@mediatek.com>
---
 drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 11 +++-
 drivers/gpu/drm/mediatek/mtk_drm_drv.c  | 79 +++++++++++++++++++++++++
 drivers/gpu/drm/mediatek/mtk_drm_drv.h  |  9 +++
 3 files changed, 97 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
index 29d0582e90e9..68b92adc96bb 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
@@ -7,7 +7,7 @@
 #include <linux/pm_runtime.h>
 
 #include <asm/barrier.h>
-
+#include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_plane_helper.h>
 #include <drm/drm_probe_helper.h>
@@ -47,6 +47,7 @@ struct mtk_drm_crtc {
 	struct mtk_disp_mutex		*mutex;
 	unsigned int			ddp_comp_nr;
 	struct mtk_ddp_comp		**ddp_comp;
+	struct drm_crtc_state		*old_crtc_state;
 };
 
 struct mtk_crtc_state {
@@ -362,6 +363,7 @@ static void mtk_crtc_ddp_hw_fini(struct mtk_drm_crtc *mtk_crtc)
 static void mtk_crtc_ddp_config(struct drm_crtc *crtc)
 {
 	struct mtk_drm_crtc *mtk_crtc = to_mtk_crtc(crtc);
+	struct drm_atomic_state *atomic_state = mtk_crtc->old_crtc_state->state;
 	struct mtk_crtc_state *state = to_mtk_crtc_state(mtk_crtc->base.state);
 	struct mtk_ddp_comp *comp = mtk_crtc->ddp_comp[0];
 	unsigned int i;
@@ -399,6 +401,7 @@ static void mtk_crtc_ddp_config(struct drm_crtc *crtc)
 			plane_state->pending.config = false;
 		}
 		mtk_crtc->pending_planes = false;
+		mtk_atomic_state_put_queue(atomic_state);
 	}
 }
 
@@ -494,6 +497,7 @@ static void mtk_drm_crtc_atomic_begin(struct drm_crtc *crtc,
 static void mtk_drm_crtc_atomic_flush(struct drm_crtc *crtc,
 				      struct drm_crtc_state *old_crtc_state)
 {
+	struct drm_atomic_state *old_atomic_state = old_crtc_state->state;
 	struct mtk_drm_crtc *mtk_crtc = to_mtk_crtc(crtc);
 	struct mtk_drm_private *priv = crtc->dev->dev_private;
 	unsigned int pending_planes = 0;
@@ -512,8 +516,11 @@ static void mtk_drm_crtc_atomic_flush(struct drm_crtc *crtc,
 			pending_planes |= BIT(i);
 		}
 	}
-	if (pending_planes)
+	if (pending_planes) {
 		mtk_crtc->pending_planes = true;
+		drm_atomic_state_get(old_atomic_state);
+		mtk_crtc->old_crtc_state = old_crtc_state;
+	}
 	if (crtc->state->color_mgmt_changed)
 		for (i = 0; i < mtk_crtc->ddp_comp_nr; i++)
 			mtk_ddp_gamma_set(mtk_crtc->ddp_comp[i], crtc->state);
diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index 6588dc6dd5e3..6c68283b6124 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -115,10 +115,85 @@ static int mtk_atomic_commit(struct drm_device *drm,
 	return 0;
 }
 
+struct mtk_atomic_state {
+	struct drm_atomic_state base;
+	struct list_head list;
+};
+
+static inline struct mtk_atomic_state *to_mtk_state(struct drm_atomic_state *s)
+{
+	return container_of(s, struct mtk_atomic_state, base);
+}
+
+void mtk_atomic_state_put_queue(struct drm_atomic_state *state)
+{
+	struct drm_device *drm = state->dev;
+	struct mtk_drm_private *mtk_drm = drm->dev_private;
+	struct mtk_atomic_state *mtk_state = to_mtk_state(state);
+	unsigned long flags;
+
+	spin_lock_irqsave(&mtk_drm->unreference.lock, flags);
+	list_add_tail(&mtk_state->list, &mtk_drm->unreference.list);
+	spin_unlock_irqrestore(&mtk_drm->unreference.lock, flags);
+
+	schedule_work(&mtk_drm->unreference.work);
+}
+
+static void mtk_unreference_work(struct work_struct *work)
+{
+	struct mtk_drm_private *mtk_drm = container_of(work,
+			struct mtk_drm_private, unreference.work);
+	unsigned long flags;
+	struct mtk_atomic_state *state, *tmp;
+
+	/*
+	 * framebuffers cannot be unreferenced in atomic context.
+	 * Therefore, only hold the spinlock when iterating unreference_list,
+	 * and drop it when doing the unreference.
+	 */
+	spin_lock_irqsave(&mtk_drm->unreference.lock, flags);
+	list_for_each_entry_safe(state, tmp, &mtk_drm->unreference.list, list) {
+		list_del(&state->list);
+		spin_unlock_irqrestore(&mtk_drm->unreference.lock, flags);
+		drm_atomic_state_put(&state->base);
+		spin_lock_irqsave(&mtk_drm->unreference.lock, flags);
+	}
+	spin_unlock_irqrestore(&mtk_drm->unreference.lock, flags);
+}
+
+static struct drm_atomic_state *
+		mtk_drm_atomic_state_alloc(struct drm_device *dev)
+{
+	struct mtk_atomic_state *mtk_state;
+
+	mtk_state = kzalloc(sizeof(*mtk_state), GFP_KERNEL);
+	if (!mtk_state)
+		return NULL;
+
+	if (drm_atomic_state_init(dev, &mtk_state->base) < 0) {
+		kfree(mtk_state);
+		return NULL;
+	}
+
+	INIT_LIST_HEAD(&mtk_state->list);
+
+	return &mtk_state->base;
+}
+
+static void mtk_drm_atomic_state_free(struct drm_atomic_state *state)
+{
+	struct mtk_atomic_state *mtk_state = to_mtk_state(state);
+
+	drm_atomic_state_default_release(state);
+	kfree(mtk_state);
+}
+
 static const struct drm_mode_config_funcs mtk_drm_mode_config_funcs = {
 	.fb_create = mtk_drm_mode_fb_create,
 	.atomic_check = drm_atomic_helper_check,
 	.atomic_commit = mtk_atomic_commit,
+	.atomic_state_alloc = mtk_drm_atomic_state_alloc,
+	.atomic_state_free = mtk_drm_atomic_state_free
 };
 
 static const enum mtk_ddp_comp_id mt2701_mtk_ddp_main[] = {
@@ -337,6 +412,10 @@ static int mtk_drm_kms_init(struct drm_device *drm)
 	drm_kms_helper_poll_init(drm);
 	drm_mode_config_reset(drm);
 
+	INIT_WORK(&private->unreference.work, mtk_unreference_work);
+	INIT_LIST_HEAD(&private->unreference.list);
+	spin_lock_init(&private->unreference.lock);
+
 	return 0;
 
 err_unset_dma_parms:
diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.h b/drivers/gpu/drm/mediatek/mtk_drm_drv.h
index b6a82728d563..c37d835cf949 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.h
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.h
@@ -55,6 +55,13 @@ struct mtk_drm_private {
 
 	struct drm_atomic_state *suspend_state;
 
+	struct {
+		struct work_struct	work;
+		struct list_head	list;
+		/* lock for unreference list */
+		spinlock_t		lock;
+	} unreference;
+
 	bool dma_parms_allocated;
 };
 
@@ -66,4 +73,6 @@ extern struct platform_driver mtk_dpi_driver;
 extern struct platform_driver mtk_dsi_driver;
 extern struct platform_driver mtk_mipi_tx_driver;
 
+void mtk_atomic_state_put_queue(struct drm_atomic_state *state);
+
 #endif /* MTK_DRM_DRV_H */
-- 
2.18.0
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