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Disable non-temporal hint on Cortex-A53/57

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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
This commit is contained in:
Sandrine Bailleux 2016-01-13 14:57:38 +00:00
parent dbc807179f
commit 54035fc467
7 changed files with 105 additions and 33 deletions
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8
Makefile
View file

@ -1,5 +1,5 @@
#
# Copyright (c) 2013-2015, ARM Limited and Contributors. All rights reserved.
# Copyright (c) 2013-2016, 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:
@ -294,9 +294,9 @@ ifneq (${ENABLE_PLAT_COMPAT}, 0)
include plat/compat/plat_compat.mk
endif
# Include the CPU specific operations makefile. By default all CPU errata
# workarounds and CPU specific optimisations are disabled. This can be
# overridden by the platform.
# Include the CPU specific operations makefile, which provides default
# values for all CPU errata workarounds and CPU specific optimisations.
# This can be overridden by the platform.
include lib/cpus/cpu-ops.mk

19
docs/cpu-specific-build-macros.md
View file

@ -26,8 +26,8 @@ by ARM. The errata workarounds are implemented for a particular revision
or a set of processor revisions. This is checked by reset handler at runtime.
Each errata workaround is identified by its `ID` as specified in the processor's
errata notice document. The format of the define used to enable/disable the
errata is `ERRATA_<Processor name>_<ID>` where the `Processor name`
is either `A57` for the `Cortex_A57` CPU or `A53` for `Cortex_A53` CPU.
errata workaround is `ERRATA_<Processor name>_<ID>`, where the `Processor name`
is for example `A57` for the `Cortex_A57` CPU.
All workarounds are disabled by default. The platform is reponsible for
enabling these workarounds according to its requirement by defining the
@ -74,6 +74,19 @@ architecture that can be enabled by the platform as desired.
sequence. Each Cortex-A57 based platform must make its own decision on
whether to use the optimization.
* `A53_DISABLE_NON_TEMPORAL_HINT`: This flag disables the cache non-temporal
hint. The LDNP/STNP instructions as implemented on Cortex-A53 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 ARM DDI 0487A.h, section D3.4.3) allows cores to ignore
the non-temporal hint and treat LDNP/STNP as LDP/STP instead. Enabling this
flag enforces this behaviour. This needs to be enabled only for revisions
<= r0p3 of the CPU and is enabled by default.
* `A57_DISABLE_NON_TEMPORAL_HINT`: This flag has the same behaviour as
`A53_DISABLE_NON_TEMPORAL_HINT` but for Cortex-A57. This needs to be
enabled only for revisions <= r1p2 of the CPU and is enabled by default.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
_Copyright (c) 2014, ARM Limited and Contributors. All rights reserved._
_Copyright (c) 2014-2016, ARM Limited and Contributors. All rights reserved._

7
include/lib/cpus/aarch64/cortex_a57.h
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2014-2015, 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:
@ -61,8 +61,9 @@
******************************************************************************/
#define CPUACTLR_EL1 S3_1_C15_C2_0 /* Instruction def. */
#define CPUACTLR_NO_ALLOC_WBWA (1 << 49)
#define CPUACTLR_DCC_AS_DCCI (1 << 44)
#define CPUACTLR_DIS_OVERREAD (1 << 52)
#define CPUACTLR_NO_ALLOC_WBWA (1 << 49)
#define CPUACTLR_DCC_AS_DCCI (1 << 44)
/*******************************************************************************
* L2 Control register specific definitions.

33
lib/cpus/aarch64/cortex_a53.S
View file

@ -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:
@ -86,33 +86,40 @@ apply_826319:
ret
endfunc errata_a53_826319_wa
/* --------------------------------------------------
* Errata Workaround for Cortex A53 Errata #836870.
* This applies only to revision <= r0p3 of Cortex A53.
* From r0p4 and onwards, this errata is enabled by
* default.
/* ---------------------------------------------------------------------
* Disable the cache non-temporal hint.
*
* This ignores the Transient allocation hint in the MAIR and treats
* allocations the same as non-transient allocation types. As a result,
* the LDNP and STNP instructions in AArch64 behave the same as the
* equivalent LDP and STP instructions.
*
* This is relevant only for revisions <= r0p3 of Cortex-A53.
* From r0p4 and onwards, the bit to disable the hint is enabled by
* default at reset.
*
* Inputs:
* x0: variant[4:7] and revision[0:3] of current cpu.
* Clobbers : x0 - x5
* --------------------------------------------------
* ---------------------------------------------------------------------
*/
func errata_a53_836870_wa
func a53_disable_non_temporal_hint
/*
* Compare x0 against revision r0p3
*/
cmp x0, #3
b.ls apply_836870
b.ls disable_hint
#if DEBUG
b print_revision_warning
#else
ret
#endif
apply_836870:
disable_hint:
mrs x1, CPUACTLR_EL1
orr x1, x1, #CPUACTLR_DTAH
msr CPUACTLR_EL1, x1
ret
endfunc errata_a53_836870_wa
endfunc a53_disable_non_temporal_hint
/* -------------------------------------------------
* The CPU Ops reset function for Cortex-A53.
@ -138,9 +145,9 @@ func cortex_a53_reset_func
bl errata_a53_826319_wa
#endif
#if ERRATA_A53_836870
#if ERRATA_A53_836870 || A53_DISABLE_NON_TEMPORAL_HINT
mov x0, x15
bl errata_a53_836870_wa
bl a53_disable_non_temporal_hint
#endif
/* ---------------------------------------------

36
lib/cpus/aarch64/cortex_a57.S
View file

@ -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:
@ -153,6 +153,35 @@ skip_813420:
ret
endfunc errata_a57_813420_wa
/* --------------------------------------------------------------------
* Disable the over-read from the LDNP instruction.
*
* This applies to all revisions <= r1p2. The performance degradation
* observed with LDNP/STNP has been fixed on r1p3 and onwards.
*
* Inputs:
* x0: variant[4:7] and revision[0:3] of current cpu.
* Clobbers : x0 - x5, x30
* ---------------------------------------------------------------------
*/
func a57_disable_ldnp_overread
/*
* Compare x0 against revision r1p2
*/
cmp x0, #0x12
b.ls disable_hint
#if DEBUG
b print_revision_warning
#else
ret
#endif
disable_hint:
mrs x1, CPUACTLR_EL1
orr x1, x1, #CPUACTLR_DIS_OVERREAD
msr CPUACTLR_EL1, x1
ret
endfunc a57_disable_ldnp_overread
/* -------------------------------------------------
* The CPU Ops reset function for Cortex-A57.
* Clobbers: x0-x5, x15, x19, x30
@ -181,6 +210,11 @@ func cortex_a57_reset_func
bl errata_a57_813420_wa
#endif
#if A57_DISABLE_NON_TEMPORAL_HINT
mov x0, x15
bl a57_disable_ldnp_overread
#endif
/* ---------------------------------------------
* As a bare minimum enable the SMP bit if it is
* not already set.

17
lib/cpus/aarch64/cpu_helpers.S
View file

@ -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:
@ -205,16 +205,17 @@ error_exit:
endfunc get_cpu_ops_ptr
#if DEBUG
/*
* This function prints a warning message to the crash console
* if the CPU revision/part number does not match the errata
* workaround enabled in the build.
* Clobber: x30, x0 - x5
*/
.section .rodata.rev_warn_str, "aS"
rev_warn_str:
.asciz "Warning: Skipping Errata workaround for non matching CPU revision number.\n"
.asciz "Warning: Skipping CPU specific reset operation for non-matching CPU revision number.\n"
/*
* This function prints the above warning message to the crash console.
* It should be called when a CPU specific operation is enabled in the
* build but doesn't apply to this CPU revision/part number.
*
* Clobber: x30, x0 - x5
*/
.globl print_revision_warning
func print_revision_warning
mov x5, x30

18
lib/cpus/cpu-ops.mk
View file

@ -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.