docs/cpu-specific-build-macros.rst - imx-atf - Git at Google

 ARM CPU Specific Build Macros
 =============================


 .. section-numbering::
     :suffix: .

 .. contents::

 This document describes the various build options present in the CPU specific
 operations framework to enable errata workarounds and to enable optimizations
 for a specific CPU on a platform.

 CPU Errata Workarounds
 ----------------------

 ARM Trusted Firmware exports a series of build flags which control the
 errata workarounds that are applied to each CPU by the reset handler. The
 errata details can be found in the CPU specific errata documents published
 by ARM:

 -  `Cortex-A53 MPCore Software Developers Errata Notice`_
 -  `Cortex-A57 MPCore Software Developers Errata Notice`_

 The errata workarounds are implemented for a particular revision or a set of
 processor revisions. This is checked by the 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 workaround is ``ERRATA_<Processor name>_<ID>``, where the ``Processor name``
 is for example ``A57`` for the ``Cortex_A57`` CPU.

 Refer to the section *CPU errata status reporting* in
 `Firmware Design guide`_ for information on to write errata workaround functions.

 All workarounds are disabled by default. The platform is responsible for
 enabling these workarounds according to its requirement by defining the
 errata workaround build flags in the platform specific makefile. In case
 these workarounds are enabled for the wrong CPU revision then the errata
 workaround is not applied. In the DEBUG build, this is indicated by
 printing a warning to the crash console.

 In the current implementation, a platform which has more than 1 variant
 with different revisions of a processor has no runtime mechanism available
 for it to specify which errata workarounds should be enabled or not.

 The value of the build flags are 0 by default, that is, disabled. Any other
 value will enable it.

 For Cortex-A53, following errata build flags are defined :

 -  ``ERRATA_A53_826319``: This applies errata 826319 workaround to Cortex-A53
    CPU. This needs to be enabled only for revision <= r0p2 of the CPU.

 -  ``ERRATA_A53_836870``: This applies errata 836870 workaround to Cortex-A53
    CPU. This needs to be enabled only for revision <= r0p3 of the CPU. From
    r0p4 and onwards, this errata is enabled by default in hardware.

 -  ``ERRATA_A53_855873``: This applies errata 855873 workaround to Cortex-A53
    CPUs. Though the erratum is present in every revision of the CPU,
    this workaround is only applied to CPUs from r0p3 onwards, which feature
    a chicken bit in CPUACTLR\_EL1 to enable a hardware workaround.
    Earlier revisions of the CPU have other errata which require the same
    workaround in software, so they should be covered anyway.

 For Cortex-A57, following errata build flags are defined :

 -  ``ERRATA_A57_806969``: This applies errata 806969 workaround to Cortex-A57
    CPU. This needs to be enabled only for revision r0p0 of the CPU.

 -  ``ERRATA_A57_813419``: This applies errata 813419 workaround to Cortex-A57
    CPU. This needs to be enabled only for revision r0p0 of the CPU.

 -  ``ERRATA_A57_813420``: This applies errata 813420 workaround to Cortex-A57
    CPU. This needs to be enabled only for revision r0p0 of the CPU.

 -  ``ERRATA_A57_826974``: This applies errata 826974 workaround to Cortex-A57
    CPU. This needs to be enabled only for revision <= r1p1 of the CPU.

 -  ``ERRATA_A57_826977``: This applies errata 826977 workaround to Cortex-A57
    CPU. This needs to be enabled only for revision <= r1p1 of the CPU.

 -  ``ERRATA_A57_828024``: This applies errata 828024 workaround to Cortex-A57
    CPU. This needs to be enabled only for revision <= r1p1 of the CPU.

 -  ``ERRATA_A57_829520``: This applies errata 829520 workaround to Cortex-A57
    CPU. This needs to be enabled only for revision <= r1p2 of the CPU.

 -  ``ERRATA_A57_833471``: This applies errata 833471 workaround to Cortex-A57
    CPU. This needs to be enabled only for revision <= r1p2 of the CPU.

 CPU Specific optimizations
 --------------------------

 This section describes some of the optimizations allowed by the CPU micro
 architecture that can be enabled by the platform as desired.

 -  ``SKIP_A57_L1_FLUSH_PWR_DWN``: This flag enables an optimization in the
    Cortex-A57 cluster power down sequence by not flushing the Level 1 data
    cache. The L1 data cache and the L2 unified cache are inclusive. A flush
    of the L2 by set/way flushes any dirty lines from the L1 as well. This
    is a known safe deviation from the Cortex-A57 TRM defined power down
    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,
    as recommended in section "4.7 Non-Temporal Loads/Stores" of the
    `Cortex-A57 Software Optimization Guide`_.

 --------------

 *Copyright (c) 2014-2016, ARM Limited and Contributors. All rights reserved.*

 .. _Cortex-A53 MPCore Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm048406/index.html
 .. _Cortex-A57 MPCore Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm049219/cortex_a57_mpcore_software_developers_errata_notice.pdf
 .. _Firmware Design guide: firmware-design.rst
 .. _Cortex-A57 Software Optimization Guide: http://infocenter.arm.com/help/topic/com.arm.doc.uan0015b/Cortex_A57_Software_Optimization_Guide_external.pdf
	ARM CPU Specific Build Macros
	=============================


	.. section-numbering::
	:suffix: .

	.. contents::

	This document describes the various build options present in the CPU specific
	operations framework to enable errata workarounds and to enable optimizations
	for a specific CPU on a platform.

	CPU Errata Workarounds
	----------------------

	ARM Trusted Firmware exports a series of build flags which control the
	errata workarounds that are applied to each CPU by the reset handler. The
	errata details can be found in the CPU specific errata documents published
	by ARM:

	- `Cortex-A53 MPCore Software Developers Errata Notice`_
	- `Cortex-A57 MPCore Software Developers Errata Notice`_

	The errata workarounds are implemented for a particular revision or a set of
	processor revisions. This is checked by the 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 workaround is ``ERRATA_<Processor name>_<ID>``, where the ``Processor name``
	is for example ``A57`` for the ``Cortex_A57`` CPU.

	Refer to the section CPU errata status reporting in
	`Firmware Design guide`_ for information on to write errata workaround functions.

	All workarounds are disabled by default. The platform is responsible for
	enabling these workarounds according to its requirement by defining the
	errata workaround build flags in the platform specific makefile. In case
	these workarounds are enabled for the wrong CPU revision then the errata
	workaround is not applied. In the DEBUG build, this is indicated by
	printing a warning to the crash console.

	In the current implementation, a platform which has more than 1 variant
	with different revisions of a processor has no runtime mechanism available
	for it to specify which errata workarounds should be enabled or not.

	The value of the build flags are 0 by default, that is, disabled. Any other
	value will enable it.

	For Cortex-A53, following errata build flags are defined :

	- ``ERRATA_A53_826319``: This applies errata 826319 workaround to Cortex-A53
	CPU. This needs to be enabled only for revision <= r0p2 of the CPU.

	- ``ERRATA_A53_836870``: This applies errata 836870 workaround to Cortex-A53
	CPU. This needs to be enabled only for revision <= r0p3 of the CPU. From
	r0p4 and onwards, this errata is enabled by default in hardware.

	- ``ERRATA_A53_855873``: This applies errata 855873 workaround to Cortex-A53
	CPUs. Though the erratum is present in every revision of the CPU,
	this workaround is only applied to CPUs from r0p3 onwards, which feature
	a chicken bit in CPUACTLR\_EL1 to enable a hardware workaround.
	Earlier revisions of the CPU have other errata which require the same
	workaround in software, so they should be covered anyway.

	For Cortex-A57, following errata build flags are defined :

	- ``ERRATA_A57_806969``: This applies errata 806969 workaround to Cortex-A57
	CPU. This needs to be enabled only for revision r0p0 of the CPU.

	- ``ERRATA_A57_813419``: This applies errata 813419 workaround to Cortex-A57
	CPU. This needs to be enabled only for revision r0p0 of the CPU.

	- ``ERRATA_A57_813420``: This applies errata 813420 workaround to Cortex-A57
	CPU. This needs to be enabled only for revision r0p0 of the CPU.

	- ``ERRATA_A57_826974``: This applies errata 826974 workaround to Cortex-A57
	CPU. This needs to be enabled only for revision <= r1p1 of the CPU.

	- ``ERRATA_A57_826977``: This applies errata 826977 workaround to Cortex-A57
	CPU. This needs to be enabled only for revision <= r1p1 of the CPU.

	- ``ERRATA_A57_828024``: This applies errata 828024 workaround to Cortex-A57
	CPU. This needs to be enabled only for revision <= r1p1 of the CPU.

	- ``ERRATA_A57_829520``: This applies errata 829520 workaround to Cortex-A57
	CPU. This needs to be enabled only for revision <= r1p2 of the CPU.

	- ``ERRATA_A57_833471``: This applies errata 833471 workaround to Cortex-A57
	CPU. This needs to be enabled only for revision <= r1p2 of the CPU.

	CPU Specific optimizations
	--------------------------

	This section describes some of the optimizations allowed by the CPU micro
	architecture that can be enabled by the platform as desired.

	- ``SKIP_A57_L1_FLUSH_PWR_DWN``: This flag enables an optimization in the
	Cortex-A57 cluster power down sequence by not flushing the Level 1 data
	cache. The L1 data cache and the L2 unified cache are inclusive. A flush
	of the L2 by set/way flushes any dirty lines from the L1 as well. This
	is a known safe deviation from the Cortex-A57 TRM defined power down
	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,
	as recommended in section "4.7 Non-Temporal Loads/Stores" of the
	`Cortex-A57 Software Optimization Guide`_.

	--------------

	Copyright (c) 2014-2016, ARM Limited and Contributors. All rights reserved.

	.. _Cortex-A53 MPCore Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm048406/index.html
	.. _Cortex-A57 MPCore Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm049219/cortex_a57_mpcore_software_developers_errata_notice.pdf
	.. _Firmware Design guide: firmware-design.rst
	.. _Cortex-A57 Software Optimization Guide: http://infocenter.arm.com/help/topic/com.arm.doc.uan0015b/Cortex_A57_Software_Optimization_Guide_external.pdf