Revert "Update FA version to 2.5.6 (#714)"

This reverts commit 965803c.

setup.py

@@ -265,7 +265,7 @@ def add_unique(l: List[str], vals: Union[str, List[str]]) -> None:
 
     # Framework-specific requirements
     if "pytorch" in frameworks():
-        add_unique(install_reqs, ["torch", "flash-attn>=2.0.6,<=2.5.6,!=2.0.9,!=2.1.0"])
+        add_unique(install_reqs, ["torch", "flash-attn>=2.0.6,<=2.4.2,!=2.0.9,!=2.1.0"])
         add_unique(test_reqs, ["numpy", "onnxruntime", "torchvision"])
     if "jax" in frameworks():
         if not found_pybind11():

transformer_engine/pytorch/attention.py

@@ -58,7 +58,6 @@
 
 _flash_attn_version = packaging.version.Version(version("flash-attn"))
 _flash_attn_version_required = packaging.version.Version("2.0.6")
-_flash_attn_max_version = packaging.version.Version("2.5.6")
 _flash_attn_2_1_plus = _flash_attn_version >= packaging.version.Version("2.1")
 _flash_attn_2_3_plus = _flash_attn_version >= packaging.version.Version("2.3")
 _flash_attn_2_4_plus = _flash_attn_version >= packaging.version.Version("2.4")
@@ -1658,9 +1657,6 @@ def __init__(
         assert (
             _flash_attn_version >= _flash_attn_version_required
         ), f"FlashAttention minimum version {_flash_attn_version_required} is required."
-        assert (
-            _flash_attn_version <= _flash_attn_max_version
-        ), f"FlashAttention maximum version {_flash_attn_max_version} is supported."
 
         self.norm_factor = norm_factor
         self.attention_dropout_ctx = attention_dropout_ctx