drm/nouveau/mc: add nvkm_mc_enabled() function

Add a function that allows us to query whether a given subdev is
currently enabled or not.
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/include/nvkm/subdev/mc.h

@@ -9,6 +9,7 @@ struct nvkm_mc {
 
 void nvkm_mc_enable(struct nvkm_device *, enum nvkm_devidx);
 void nvkm_mc_disable(struct nvkm_device *, enum nvkm_devidx);
+bool nvkm_mc_enabled(struct nvkm_device *, enum nvkm_devidx);
 void nvkm_mc_reset(struct nvkm_device *, enum nvkm_devidx);
 void nvkm_mc_intr(struct nvkm_device *, bool *handled);
 void nvkm_mc_intr_unarm(struct nvkm_device *);

drivers/gpu/drm/nouveau/nvkm/subdev/mc/base.c

@@ -161,6 +161,16 @@ nvkm_mc_enable(struct nvkm_device *device, enum nvkm_devidx devidx)
 	}
 }
 
+bool
+nvkm_mc_enabled(struct nvkm_device *device, enum nvkm_devidx devidx)
+{
+	u64 pmc_enable = nvkm_mc_reset_mask(device, false, devidx);
+
+	return (pmc_enable != 0) &&
+	       ((nvkm_rd32(device, 0x000200) & pmc_enable) == pmc_enable);
+}
+
+
 static int
 nvkm_mc_fini(struct nvkm_subdev *subdev, bool suspend)
 {