linux-kernel - [PATCH] drm/mediatek: Add wait_event

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Message-ID: <20250522085149.3361598-1-jason-jh.lin@mediatek.com>
Date: Thu, 22 May 2025 16:34:24 +0800
From: Jason-JH Lin <jason-jh.lin@...iatek.com>
To: Chun-Kuang Hu <chunkuang.hu@...nel.org>, AngeloGioacchino Del Regno
	<angelogioacchino.delregno@...labora.com>
CC: "Jason-JH . Lin" <jason-jh.lin@...iatek.com>, Nancy Lin
	<nancy.lin@...iatek.com>, Singo Chang <singo.chang@...iatek.com>, Paul-PL
 Chen <paul-pl.chen@...iatek.com>, Yongqiang Niu <yongqiang.niu@...iatek.com>,
	Zhenxing Qin <zhenxing.qin@...iatek.com>, Sirius Wang
	<sirius.wang@...iatek.com>, Xavier Chang <xavier.chang@...iatek.com>, Fei
 Shao <fshao@...omium.org>, Chen-yu Tsai <wenst@...omium.org>,
	<dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
	<linux-mediatek@...ts.infradead.org>, <linux-arm-kernel@...ts.infradead.org>,
	<Project_Global_Chrome_Upstream_Group@...iatek.com>
Subject: [PATCH] drm/mediatek: Add wait_event_timeout when disabling plane

Our hardware registers are set through GCE, not by the CPU.
DRM might assume the hardware is disabled immediately after calling
atomic_disable() of drm_plane, but it is only truly disabled after the
GCE IRQ is triggered.

Additionally, the cursor plane in DRM uses async_commit, so DRM will
not wait for vblank and will free the buffer immediately after calling
atomic_disable().

To prevent the framebuffer from being freed before the layer disable
settings are configured into the hardware, which can cause an IOMMU
fault error, a wait_event_timeout has been added to wait for the
ddp_cmdq_cb() callback,indicating that the GCE IRQ has been triggered.

Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.")
Signed-off-by: Jason-JH Lin <jason-jh.lin@...iatek.com>
---
 drivers/gpu/drm/mediatek/mtk_crtc.c  | 30 ++++++++++++++++++++++++++++
 drivers/gpu/drm/mediatek/mtk_crtc.h  |  1 +
 drivers/gpu/drm/mediatek/mtk_plane.c |  5 +++++
 3 files changed, 36 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_crtc.c b/drivers/gpu/drm/mediatek/mtk_crtc.c
index 8f6fba4217ec..944a3d1e5ec9 100644
--- a/drivers/gpu/drm/mediatek/mtk_crtc.c
+++ b/drivers/gpu/drm/mediatek/mtk_crtc.c
@@ -719,6 +719,36 @@ int mtk_crtc_plane_check(struct drm_crtc *crtc, struct drm_plane *plane,
 	return 0;
 }
 
+void mtk_crtc_plane_disable(struct drm_crtc *crtc, struct drm_plane *plane)
+{
+	struct mtk_crtc *mtk_crtc = to_mtk_crtc(crtc);
+	struct mtk_plane_state *plane_state = to_mtk_plane_state(plane->state);
+	int i;
+
+	if (!mtk_crtc->enabled)
+		return;
+
+	/* set pending plane state to disabled */
+	for (i = 0; i < mtk_crtc->layer_nr; i++) {
+		struct drm_plane *mtk_plane = &mtk_crtc->planes[i];
+		struct mtk_plane_state *mtk_plane_state = to_mtk_plane_state(mtk_plane->state);
+
+		if (mtk_plane->index == plane->index) {
+			memcpy(mtk_plane_state, plane_state, sizeof(*plane_state));
+			break;
+		}
+	}
+	mtk_crtc_update_config(mtk_crtc, false);
+
+#if IS_REACHABLE(CONFIG_MTK_CMDQ)
+	/* wait for planes to be disabled by cmdq */
+	if (mtk_crtc->cmdq_client.chan)
+		wait_event_timeout(mtk_crtc->cb_blocking_queue,
+				   mtk_crtc->cmdq_vblank_cnt == 0,
+				   msecs_to_jiffies(500));
+#endif
+}
+
 void mtk_crtc_async_update(struct drm_crtc *crtc, struct drm_plane *plane,
 			   struct drm_atomic_state *state)
 {
diff --git a/drivers/gpu/drm/mediatek/mtk_crtc.h b/drivers/gpu/drm/mediatek/mtk_crtc.h
index 388e900b6f4d..828f109b83e7 100644
--- a/drivers/gpu/drm/mediatek/mtk_crtc.h
+++ b/drivers/gpu/drm/mediatek/mtk_crtc.h
@@ -21,6 +21,7 @@ int mtk_crtc_create(struct drm_device *drm_dev, const unsigned int *path,
 		    unsigned int num_conn_routes);
 int mtk_crtc_plane_check(struct drm_crtc *crtc, struct drm_plane *plane,
 			 struct mtk_plane_state *state);
+void mtk_crtc_plane_disable(struct drm_crtc *crtc, struct drm_plane *plane);
 void mtk_crtc_async_update(struct drm_crtc *crtc, struct drm_plane *plane,
 			   struct drm_atomic_state *plane_state);
 struct device *mtk_crtc_dma_dev_get(struct drm_crtc *crtc);
diff --git a/drivers/gpu/drm/mediatek/mtk_plane.c b/drivers/gpu/drm/mediatek/mtk_plane.c
index 655106bbb76d..59edbe26f01e 100644
--- a/drivers/gpu/drm/mediatek/mtk_plane.c
+++ b/drivers/gpu/drm/mediatek/mtk_plane.c
@@ -285,9 +285,14 @@ static void mtk_plane_atomic_disable(struct drm_plane *plane,
 	struct drm_plane_state *new_state = drm_atomic_get_new_plane_state(state,
 									   plane);
 	struct mtk_plane_state *mtk_plane_state = to_mtk_plane_state(new_state);
+	struct drm_plane_state *old_state = drm_atomic_get_old_plane_state(state,
+									   plane);
+
 	mtk_plane_state->pending.enable = false;
 	wmb(); /* Make sure the above parameter is set before update */
 	mtk_plane_state->pending.dirty = true;
+
+	mtk_crtc_plane_disable(old_state->crtc, plane);
 }
 
 static void mtk_plane_atomic_update(struct drm_plane *plane,
-- 
2.43.0