[Misc] Add a wrapper for torch.inference_mode (#6618)

vllm/platforms/__init__.py

@@ -2,7 +2,9 @@ from typing import Optional
 
 import torch
 
-from .interface import Platform, PlatformEnum
+from vllm.utils import is_tpu
+
+from .interface import Platform, PlatformEnum, UnspecifiedPlatform
 
 current_platform: Optional[Platform]
 
@@ -12,7 +14,10 @@ if torch.version.cuda is not None:
 elif torch.version.hip is not None:
     from .rocm import RocmPlatform
     current_platform = RocmPlatform()
+elif is_tpu():
+    from .tpu import TpuPlatform
+    current_platform = TpuPlatform()
 else:
-    current_platform = None
+    current_platform = UnspecifiedPlatform()
 
 __all__ = ['Platform', 'PlatformEnum', 'current_platform']