drm/nouveau/dispnv50: Don't call drm_atomic_get_crtc_state() in prepare_fb

Since we recently started warning about uses of this function after the
atomic check phase completes, we've started getting warnings about this in
nouveau. It appears a misplaced drm_atomic_get_crtc_state() call has been
hiding in our .prepare_fb callback for a while.

So, fix this by adding a new nv50_head_atom_get_new() function and use that
in our .prepare_fb callback instead.

Signed-off-by: Lyude Paul <[e-mail]>
Reviewed-by: Dave Airlie <[e-mail]>
Fixes: 1590700d94ac ("drm/nouveau/kms/nv50-: split each resource type into their own source files")
Cc: <[e-mail]> # v4.18+
Link: https://patch.msgid.link/[e-mail]

drivers/gpu/drm/nouveau/dispnv50/atom.h

···
 nv50_head_atom_get(struct drm_atomic_state *state, struct drm_crtc *crtc)
 {
 	struct drm_crtc_state *statec = drm_atomic_get_crtc_state(state, crtc);
+
 	if (IS_ERR(statec))
 		return (void *)statec;
+
+	return nv50_head_atom(statec);
+}
+
+static inline struct nv50_head_atom *
+nv50_head_atom_get_new(struct drm_atomic_state *state, struct drm_crtc *crtc)
+{
+	struct drm_crtc_state *statec = drm_atomic_get_new_crtc_state(state, crtc);
+
+	if (!statec)
+		return NULL;
+
 	return nv50_head_atom(statec);
 }
 

drivers/gpu/drm/nouveau/dispnv50/wndw.c

···
 	asyw->image.offset[0] = nvbo->offset;
 
 	if (wndw->func->prepare) {
-		asyh = nv50_head_atom_get(asyw->state.state, asyw->state.crtc);
+		asyh = nv50_head_atom_get_new(asyw->state.state, asyw->state.crtc);
 		if (IS_ERR(asyh))
 			return PTR_ERR(asyh);