Disable non-temporal hint on Cortex-A53/57
The LDNP/STNP instructions as implemented on Cortex-A53 and
Cortex-A57 do not behave in a way most programmers expect, and will
most probably result in a significant speed degradation to any code
that employs them. The ARMv8-A architecture (see Document ARM DDI
0487A.h, section D3.4.3) allows cores to ignore the non-temporal hint
and treat LDNP/STNP as LDP/STP instead.
This patch introduces 2 new build flags:
A53_DISABLE_NON_TEMPORAL_HINT and A57_DISABLE_NON_TEMPORAL_HINT
to enforce this behaviour on Cortex-A53 and Cortex-A57. They are
enabled by default.
The string printed in debug builds when a specific CPU errata
workaround is compiled in but skipped at runtime has been
generalised, so that it can be reused for the non-temporal hint use
case as well.
Change-Id: I3e354f4797fd5d3959872a678e160322b13867a1
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index a872360..a3a08e1 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -1,5 +1,5 @@
#
-# Copyright (c) 2014, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2014-2016, ARM Limited and Contributors. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
@@ -32,10 +32,26 @@
# cluster is powered down.
SKIP_A57_L1_FLUSH_PWR_DWN ?=0
+# Flag to disable the cache non-temporal hint.
+# It is enabled by default.
+A53_DISABLE_NON_TEMPORAL_HINT ?=1
+
+# Flag to disable the cache non-temporal hint.
+# It is enabled by default.
+A57_DISABLE_NON_TEMPORAL_HINT ?=1
+
# Process SKIP_A57_L1_FLUSH_PWR_DWN flag
$(eval $(call assert_boolean,SKIP_A57_L1_FLUSH_PWR_DWN))
$(eval $(call add_define,SKIP_A57_L1_FLUSH_PWR_DWN))
+# Process A53_DISABLE_NON_TEMPORAL_HINT flag
+$(eval $(call assert_boolean,A53_DISABLE_NON_TEMPORAL_HINT))
+$(eval $(call add_define,A53_DISABLE_NON_TEMPORAL_HINT))
+
+# Process A57_DISABLE_NON_TEMPORAL_HINT flag
+$(eval $(call assert_boolean,A57_DISABLE_NON_TEMPORAL_HINT))
+$(eval $(call add_define,A57_DISABLE_NON_TEMPORAL_HINT))
+
# CPU Errata Build flags. These should be enabled by the
# platform if the errata needs to be applied.