[PATCH] drm/mediatek: Add wait_event_timeout when disabling plane

Jason-JH Lin
2025-05-22T08:59:37Z

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@mediatek.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