Having a fence linked to a virtio_gpu_framebuffer in the plane update sequence
would cause conflict when several planes referencing the same framebuffer
(e.g. Xorg screen covering multi-displays configured for an extended mode)
and those planes are updated concurrently. So it is needed to allocate a
fence for every plane state instead of the framebuffer.

The plane state for virtio-gpu, "struct virtio_gpu_plane_state" is added for
this. This structure represents drm_plane_state and it contains the reference
to virtio_gpu_fence, which was previously in "struct virtio_gpu_framebuffer".

"virtio_gpu_plane_duplicate_state" is added as well to create a
virtio_gpu_plane_state on top of duplicated drm plane state.

Several drm helpers were slightly modified accordingly to use the fence in new
plane state structure. virtio_gpu_plane_cleanup_fb was completely removed as
dma_fence_put shouldn't be called here as it can mess up with the ref count
of the fence. The fence should be put after the fence is signaled in
virtio_gpu_resource_flush then released in virtio_gpu_array_add_fence while
the next virtio message is being queued.

Also, the condition for adding fence, (plane->state->fb != new_state->fb) was
removed since we now allocate a new fence for the new plane state even if both
old and new planes are pointing to the same framebuffer.

v2: removed virtio_gpu_plane_duplicate_state as the existing helper,
    drm_atomic_helper_plane_destroy_state does the same.

Cc: Dmitry Osipenko <dmitry.osipe...@collabora.com>
Cc: Gerd Hoffmann <kra...@redhat.com>
Cc: Vivek Kasireddy <vivek.kasire...@intel.com>
Signed-off-by: Dongwon Kim <dongwon....@intel.com>
---
 drivers/gpu/drm/virtio/virtgpu_drv.h   |  7 +++
 drivers/gpu/drm/virtio/virtgpu_plane.c | 66 +++++++++++++++++---------
 2 files changed, 51 insertions(+), 22 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h 
b/drivers/gpu/drm/virtio/virtgpu_drv.h
index 8513b671f871..2568ad0c2d44 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.h
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
@@ -191,6 +191,13 @@ struct virtio_gpu_framebuffer {
 #define to_virtio_gpu_framebuffer(x) \
        container_of(x, struct virtio_gpu_framebuffer, base)
 
+struct virtio_gpu_plane_state {
+       struct drm_plane_state base;
+       struct virtio_gpu_fence *fence;
+};
+#define to_virtio_gpu_plane_state(x) \
+       container_of(x, struct virtio_gpu_plane_state, base)
+
 struct virtio_gpu_queue {
        struct virtqueue *vq;
        spinlock_t qlock;
diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c 
b/drivers/gpu/drm/virtio/virtgpu_plane.c
index a2e045f3a000..cd962898023e 100644
--- a/drivers/gpu/drm/virtio/virtgpu_plane.c
+++ b/drivers/gpu/drm/virtio/virtgpu_plane.c
@@ -66,11 +66,28 @@ uint32_t virtio_gpu_translate_format(uint32_t drm_fourcc)
        return format;
 }
 
+static struct
+drm_plane_state *virtio_gpu_plane_duplicate_state(struct drm_plane *plane)
+{
+       struct virtio_gpu_plane_state *new;
+
+       if (WARN_ON(!plane->state))
+               return NULL;
+
+       new = kzalloc(sizeof(*new), GFP_KERNEL);
+       if (!new)
+               return NULL;
+
+       __drm_atomic_helper_plane_duplicate_state(plane, &new->base);
+
+       return &new->base;
+}
+
 static const struct drm_plane_funcs virtio_gpu_plane_funcs = {
        .update_plane           = drm_atomic_helper_update_plane,
        .disable_plane          = drm_atomic_helper_disable_plane,
        .reset                  = drm_atomic_helper_plane_reset,
-       .atomic_duplicate_state = drm_atomic_helper_plane_duplicate_state,
+       .atomic_duplicate_state = virtio_gpu_plane_duplicate_state,
        .atomic_destroy_state   = drm_atomic_helper_plane_destroy_state,
 };
 
@@ -128,11 +145,13 @@ static void virtio_gpu_resource_flush(struct drm_plane 
*plane,
        struct drm_device *dev = plane->dev;
        struct virtio_gpu_device *vgdev = dev->dev_private;
        struct virtio_gpu_framebuffer *vgfb;
+       struct virtio_gpu_plane_state *vgplane_st;
        struct virtio_gpu_object *bo;
 
        vgfb = to_virtio_gpu_framebuffer(plane->state->fb);
+       vgplane_st = to_virtio_gpu_plane_state(plane->state);
        bo = gem_to_virtio_gpu_obj(vgfb->base.obj[0]);
-       if (vgfb->fence) {
+       if (vgplane_st->fence) {
                struct virtio_gpu_object_array *objs;
 
                objs = virtio_gpu_array_alloc(1);
@@ -141,13 +160,12 @@ static void virtio_gpu_resource_flush(struct drm_plane 
*plane,
                virtio_gpu_array_add_obj(objs, vgfb->base.obj[0]);
                virtio_gpu_array_lock_resv(objs);
                virtio_gpu_cmd_resource_flush(vgdev, bo->hw_res_handle, x, y,
-                                             width, height, objs, vgfb->fence);
+                                             width, height, objs,
+                                             vgplane_st->fence);
                virtio_gpu_notify(vgdev);
-
-               dma_fence_wait_timeout(&vgfb->fence->f, true,
+               dma_fence_wait_timeout(&vgplane_st->fence->f, true,
                                       msecs_to_jiffies(50));
-               dma_fence_put(&vgfb->fence->f);
-               vgfb->fence = NULL;
+               dma_fence_put(&vgplane_st->fence->f);
        } else {
                virtio_gpu_cmd_resource_flush(vgdev, bo->hw_res_handle, x, y,
                                              width, height, NULL, NULL);
@@ -237,20 +255,23 @@ static int virtio_gpu_plane_prepare_fb(struct drm_plane 
*plane,
        struct drm_device *dev = plane->dev;
        struct virtio_gpu_device *vgdev = dev->dev_private;
        struct virtio_gpu_framebuffer *vgfb;
+       struct virtio_gpu_plane_state *vgplane_st;
        struct virtio_gpu_object *bo;
 
        if (!new_state->fb)
                return 0;
 
        vgfb = to_virtio_gpu_framebuffer(new_state->fb);
+       vgplane_st = to_virtio_gpu_plane_state(new_state);
        bo = gem_to_virtio_gpu_obj(vgfb->base.obj[0]);
        if (!bo || (plane->type == DRM_PLANE_TYPE_PRIMARY && !bo->guest_blob))
                return 0;
 
-       if (bo->dumb && (plane->state->fb != new_state->fb)) {
-               vgfb->fence = virtio_gpu_fence_alloc(vgdev, 
vgdev->fence_drv.context,
+       if (bo->dumb) {
+               vgplane_st->fence = virtio_gpu_fence_alloc(vgdev,
+                                                    vgdev->fence_drv.context,
                                                     0);
-               if (!vgfb->fence)
+               if (!vgplane_st->fence)
                        return -ENOMEM;
        }
 
@@ -258,17 +279,17 @@ static int virtio_gpu_plane_prepare_fb(struct drm_plane 
*plane,
 }
 
 static void virtio_gpu_plane_cleanup_fb(struct drm_plane *plane,
-                                       struct drm_plane_state *state)
+                                        struct drm_plane_state *state)
 {
-       struct virtio_gpu_framebuffer *vgfb;
+       struct virtio_gpu_plane_state *vgplane_st;
 
        if (!state->fb)
                return;
 
-       vgfb = to_virtio_gpu_framebuffer(state->fb);
-       if (vgfb->fence) {
-               dma_fence_put(&vgfb->fence->f);
-               vgfb->fence = NULL;
+       vgplane_st = to_virtio_gpu_plane_state(state);
+       if (vgplane_st->fence) {
+               dma_fence_put(&vgplane_st->fence->f);
+               vgplane_st->fence = NULL;
        }
 }
 
@@ -281,6 +302,7 @@ static void virtio_gpu_cursor_plane_update(struct drm_plane 
*plane,
        struct virtio_gpu_device *vgdev = dev->dev_private;
        struct virtio_gpu_output *output = NULL;
        struct virtio_gpu_framebuffer *vgfb;
+       struct virtio_gpu_plane_state *vgplane_st;
        struct virtio_gpu_object *bo = NULL;
        uint32_t handle;
 
@@ -293,6 +315,7 @@ static void virtio_gpu_cursor_plane_update(struct drm_plane 
*plane,
 
        if (plane->state->fb) {
                vgfb = to_virtio_gpu_framebuffer(plane->state->fb);
+               vgplane_st = to_virtio_gpu_plane_state(plane->state);
                bo = gem_to_virtio_gpu_obj(vgfb->base.obj[0]);
                handle = bo->hw_res_handle;
        } else {
@@ -312,11 +335,10 @@ static void virtio_gpu_cursor_plane_update(struct 
drm_plane *plane,
                        (vgdev, 0,
                         plane->state->crtc_w,
                         plane->state->crtc_h,
-                        0, 0, objs, vgfb->fence);
+                        0, 0, objs, vgplane_st->fence);
                virtio_gpu_notify(vgdev);
-               dma_fence_wait(&vgfb->fence->f, true);
-               dma_fence_put(&vgfb->fence->f);
-               vgfb->fence = NULL;
+               dma_fence_wait(&vgplane_st->fence->f, true);
+               dma_fence_put(&vgplane_st->fence->f);
        }
 
        if (plane->state->fb != old_state->fb) {
@@ -351,14 +373,14 @@ static void virtio_gpu_cursor_plane_update(struct 
drm_plane *plane,
 
 static const struct drm_plane_helper_funcs virtio_gpu_primary_helper_funcs = {
        .prepare_fb             = virtio_gpu_plane_prepare_fb,
-       .cleanup_fb             = virtio_gpu_plane_cleanup_fb,
+       .cleanup_fb             = virtio_gpu_plane_cleanup_fb,
        .atomic_check           = virtio_gpu_plane_atomic_check,
        .atomic_update          = virtio_gpu_primary_plane_update,
 };
 
 static const struct drm_plane_helper_funcs virtio_gpu_cursor_helper_funcs = {
        .prepare_fb             = virtio_gpu_plane_prepare_fb,
-       .cleanup_fb             = virtio_gpu_plane_cleanup_fb,
+       .cleanup_fb             = virtio_gpu_plane_cleanup_fb,
        .atomic_check           = virtio_gpu_plane_atomic_check,
        .atomic_update          = virtio_gpu_cursor_plane_update,
 };
-- 
2.20.1

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