drm/msm/dpu: Propagate error from dpu_assign_plane_resources

The dpu_plane_virtual_assign_resources function might fail if there is
no suitable SSPP(s) for the plane. This leaves sspp field in plane
state uninitialized and later leads to NULL dereference during commit:

Call trace:
 _dpu_crtc_blend_setup+0x194/0x620 [msm] (P)
 dpu_crtc_atomic_begin+0xe4/0x240 [msm]
 drm_atomic_helper_commit_planes+0x88/0x358
 msm_atomic_commit_tail+0x1b4/0x8b8 [msm]
 commit_tail+0xa8/0x1b0
 drm_atomic_helper_commit+0x180/0x1a0
 drm_atomic_commit+0x94/0xe0
 drm_mode_atomic_ioctl+0xa88/0xd60
 drm_ioctl_kernel+0xc4/0x138
 drm_ioctl+0x364/0x4f0
 __arm64_sys_ioctl+0xac/0x108
 invoke_syscall.constprop.0+0x48/0x100
 el0_svc_common.constprop.0+0x40/0xe8
 do_el0_svc+0x24/0x38
 el0_svc+0x30/0xe0
 el0t_64_sync_handler+0xa0/0xe8
 el0t_64_sync+0x198/0x1a0

Fixes: 3ed12a3 ("drm/msm/dpu: allow sharing SSPP between planes")
Signed-off-by: Vladimir Lypak <[email protected]>
Reviewed-by: Dmitry Baryshkov <[email protected]>
Patchwork: https://patchwork.freedesktop.org/patch/681916/
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Dmitry Baryshkov <[email protected]>

Author: vldly

drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c

@@ -1278,7 +1278,7 @@ int dpu_assign_plane_resources(struct dpu_global_state *global_state,
 							     state, plane_state,
 							     prev_adjacent_plane_state);
 		if (ret)
-			break;
+			return ret;
 
 		prev_adjacent_plane_state = plane_state;
 	}