drm/nouveau/bar/nv50: ensure BAR is mapped

If the BAR is zero size, it indicates it was never successfully mapped.
Ensure that the BAR is valid during initialization before attempting to
use it.
Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nvkm/subdev/bar/nv50.c

@@ -109,7 +109,7 @@ nv50_bar_oneinit(struct nvkm_bar *base)
 	struct nvkm_device *device = bar->base.subdev.device;
 	static struct lock_class_key bar1_lock;
 	static struct lock_class_key bar2_lock;
-	u64 start, limit;
+	u64 start, limit, size;
 	int ret;
 
 	ret = nvkm_gpuobj_new(device, 0x20000, 0, false, NULL, &bar->mem);
@@ -127,7 +127,10 @@ nv50_bar_oneinit(struct nvkm_bar *base)
 
 	/* BAR2 */
 	start = 0x0100000000ULL;
-	limit = start + device->func->resource_size(device, 3);
+	size = device->func->resource_size(device, 3);
+	if (!size)
+		return -ENOMEM;
+	limit = start + size;
 
 	ret = nvkm_vmm_new(device, start, limit-- - start, NULL, 0,
 			   &bar2_lock, "bar2", &bar->bar2_vmm);
@@ -164,7 +167,10 @@ nv50_bar_oneinit(struct nvkm_bar *base)
 
 	/* BAR1 */
 	start = 0x0000000000ULL;
-	limit = start + device->func->resource_size(device, 1);
+	size = device->func->resource_size(device, 1);
+	if (!size)
+		return -ENOMEM;
+	limit = start + size;
 
 	ret = nvkm_vmm_new(device, start, limit-- - start, NULL, 0,
 			   &bar1_lock, "bar1", &bar->bar1_vmm);