drm/vc4: Make sure that the v3d ident debugfs has vc4's power on.

Otherwise, you sometimes decode the ident fields based on 0xdeadbeef
register reads.
Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20190220210343.28157-7-eric@anholt.netReviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>

drivers/gpu/drm/vc4/vc4_v3d.c

@@ -121,6 +121,9 @@ int vc4_v3d_debugfs_ident(struct seq_file *m, void *unused)
 	struct drm_info_node *node = (struct drm_info_node *)m->private;
 	struct drm_device *dev = node->minor->dev;
 	struct vc4_dev *vc4 = to_vc4_dev(dev);
+	int ret = vc4_v3d_pm_get(vc4);
+
+	if (ret == 0) {
 		uint32_t ident1 = V3D_READ(V3D_IDENT1);
 		uint32_t nslc = VC4_GET_FIELD(ident1, V3D_IDENT1_NSLC);
 		uint32_t tups = VC4_GET_FIELD(ident1, V3D_IDENT1_TUPS);
@@ -133,6 +136,8 @@ int vc4_v3d_debugfs_ident(struct seq_file *m, void *unused)
 		seq_printf(m, "QPUs:       %d\n", nslc * qups);
 		seq_printf(m, "Semaphores: %d\n",
 			   VC4_GET_FIELD(ident1, V3D_IDENT1_NSEM));
+		vc4_v3d_pm_put(vc4);
+	}
 
 	return 0;
 }