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Arm CPU Specific Build Macros
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=============================
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This document describes the various build options present in the CPU specific
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operations framework to enable errata workarounds and to enable optimizations
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for a specific CPU on a platform.
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Security Vulnerability Workarounds
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----------------------------------
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TF-A exports a series of build flags which control which security
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vulnerability workarounds should be applied at runtime.
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- ``WORKAROUND_CVE_2017_5715``: Enables the security workaround for
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`CVE-2017-5715`_. This flag can be set to 0 by the platform if none
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of the PEs in the system need the workaround. Setting this flag to 0 provides
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no performance benefit for non-affected platforms, it just helps to comply
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with the recommendation in the spec regarding workaround discovery.
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Defaults to 1.
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- ``WORKAROUND_CVE_2018_3639``: Enables the security workaround for
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`CVE-2018-3639`_. Defaults to 1. The TF-A project recommends to keep
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the default value of 1 even on platforms that are unaffected by
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CVE-2018-3639, in order to comply with the recommendation in the spec
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regarding workaround discovery.
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- ``DYNAMIC_WORKAROUND_CVE_2018_3639``: Enables dynamic mitigation for
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`CVE-2018-3639`_. This build option should be set to 1 if the target
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platform contains at least 1 CPU that requires dynamic mitigation.
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Defaults to 0.
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CPU Errata Workarounds
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----------------------
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TF-A exports a series of build flags which control the errata workarounds that
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are applied to each CPU by the reset handler. The errata details can be found
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in the CPU specific errata documents published by Arm:
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- `Cortex-A53 MPCore Software Developers Errata Notice`_
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- `Cortex-A57 MPCore Software Developers Errata Notice`_
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- `Cortex-A72 MPCore Software Developers Errata Notice`_
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The errata workarounds are implemented for a particular revision or a set of
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processor revisions. This is checked by the reset handler at runtime. Each
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errata workaround is identified by its ``ID`` as specified in the processor's
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errata notice document. The format of the define used to enable/disable the
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errata workaround is ``ERRATA_<Processor name>_<ID>``, where the ``Processor name``
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is for example ``A57`` for the ``Cortex_A57`` CPU.
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Refer to the section *CPU errata status reporting* in
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`Firmware Design guide`_ for information on how to write errata workaround
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functions.
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All workarounds are disabled by default. The platform is responsible for
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enabling these workarounds according to its requirement by defining the
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errata workaround build flags in the platform specific makefile. In case
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these workarounds are enabled for the wrong CPU revision then the errata
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workaround is not applied. In the DEBUG build, this is indicated by
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printing a warning to the crash console.
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In the current implementation, a platform which has more than 1 variant
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with different revisions of a processor has no runtime mechanism available
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for it to specify which errata workarounds should be enabled or not.
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The value of the build flags is 0 by default, that is, disabled. A value of 1
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will enable it.
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For Cortex-A9, the following errata build flags are defined :
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- ``ERRATA_A9_794073``: This applies errata 794073 workaround to Cortex-A9
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CPU. This needs to be enabled for all revisions of the CPU.
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For Cortex-A15, the following errata build flags are defined :
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- ``ERRATA_A15_816470``: This applies errata 816470 workaround to Cortex-A15
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CPU. This needs to be enabled only for revision >= r3p0 of the CPU.
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- ``ERRATA_A15_827671``: This applies errata 827671 workaround to Cortex-A15
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CPU. This needs to be enabled only for revision >= r3p0 of the CPU.
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For Cortex-A17, the following errata build flags are defined :
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- ``ERRATA_A17_852421``: This applies errata 852421 workaround to Cortex-A17
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CPU. This needs to be enabled only for revision <= r1p2 of the CPU.
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- ``ERRATA_A17_852423``: This applies errata 852423 workaround to Cortex-A17
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CPU. This needs to be enabled only for revision <= r1p2 of the CPU.
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For Cortex-A35, the following errata build flags are defined :
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- ``ERRATA_A35_855472``: This applies errata 855472 workaround to Cortex-A35
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CPUs. This needs to be enabled only for revision r0p0 of Cortex-A35.
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For Cortex-A53, the following errata build flags are defined :
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- ``ERRATA_A53_819472``: This applies errata 819472 workaround to all
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CPUs. This needs to be enabled only for revision <= r0p1 of Cortex-A53.
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- ``ERRATA_A53_824069``: This applies errata 824069 workaround to all
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CPUs. This needs to be enabled only for revision <= r0p2 of Cortex-A53.
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- ``ERRATA_A53_826319``: This applies errata 826319 workaround to Cortex-A53
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CPU. This needs to be enabled only for revision <= r0p2 of the CPU.
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- ``ERRATA_A53_827319``: This applies errata 827319 workaround to all
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CPUs. This needs to be enabled only for revision <= r0p2 of Cortex-A53.
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- ``ERRATA_A53_835769``: This applies erratum 835769 workaround at compile and
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link time to Cortex-A53 CPU. This needs to be enabled for some variants of
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revision <= r0p4. This workaround can lead the linker to create ``*.stub``
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sections.
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- ``ERRATA_A53_836870``: This applies errata 836870 workaround to Cortex-A53
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CPU. This needs to be enabled only for revision <= r0p3 of the CPU. From
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r0p4 and onwards, this errata is enabled by default in hardware.
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- ``ERRATA_A53_843419``: This applies erratum 843419 workaround at link time
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to Cortex-A53 CPU. This needs to be enabled for some variants of revision
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<= r0p4. This workaround can lead the linker to emit ``*.stub`` sections
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which are 4kB aligned.
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- ``ERRATA_A53_855873``: This applies errata 855873 workaround to Cortex-A53
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CPUs. Though the erratum is present in every revision of the CPU,
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this workaround is only applied to CPUs from r0p3 onwards, which feature
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a chicken bit in CPUACTLR_EL1 to enable a hardware workaround.
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Earlier revisions of the CPU have other errata which require the same
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workaround in software, so they should be covered anyway.
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For Cortex-A55, the following errata build flags are defined :
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- ``ERRATA_A55_768277``: This applies errata 768277 workaround to Cortex-A55
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CPU. This needs to be enabled only for revision r0p0 of the CPU.
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- ``ERRATA_A55_778703``: This applies errata 778703 workaround to Cortex-A55
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CPU. This needs to be enabled only for revision r0p0 of the CPU.
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- ``ERRATA_A55_798797``: This applies errata 798797 workaround to Cortex-A55
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CPU. This needs to be enabled only for revision r0p0 of the CPU.
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- ``ERRATA_A55_846532``: This applies errata 846532 workaround to Cortex-A55
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CPU. This needs to be enabled only for revision <= r0p1 of the CPU.
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- ``ERRATA_A55_903758``: This applies errata 903758 workaround to Cortex-A55
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CPU. This needs to be enabled only for revision <= r0p1 of the CPU.
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- ``ERRATA_A55_1221012``: This applies errata 1221012 workaround to Cortex-A55
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CPU. This needs to be enabled only for revision <= r1p0 of the CPU.
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For Cortex-A57, the following errata build flags are defined :
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- ``ERRATA_A57_806969``: This applies errata 806969 workaround to Cortex-A57
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CPU. This needs to be enabled only for revision r0p0 of the CPU.
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- ``ERRATA_A57_813419``: This applies errata 813419 workaround to Cortex-A57
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CPU. This needs to be enabled only for revision r0p0 of the CPU.
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- ``ERRATA_A57_813420``: This applies errata 813420 workaround to Cortex-A57
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CPU. This needs to be enabled only for revision r0p0 of the CPU.
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- ``ERRATA_A57_814670``: This applies errata 814670 workaround to Cortex-A57
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CPU. This needs to be enabled only for revision r0p0 of the CPU.
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- ``ERRATA_A57_817169``: This applies errata 817169 workaround to Cortex-A57
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CPU. This needs to be enabled only for revision <= r0p1 of the CPU.
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- ``ERRATA_A57_826974``: This applies errata 826974 workaround to Cortex-A57
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CPU. This needs to be enabled only for revision <= r1p1 of the CPU.
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- ``ERRATA_A57_826977``: This applies errata 826977 workaround to Cortex-A57
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CPU. This needs to be enabled only for revision <= r1p1 of the CPU.
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- ``ERRATA_A57_828024``: This applies errata 828024 workaround to Cortex-A57
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CPU. This needs to be enabled only for revision <= r1p1 of the CPU.
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- ``ERRATA_A57_829520``: This applies errata 829520 workaround to Cortex-A57
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CPU. This needs to be enabled only for revision <= r1p2 of the CPU.
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- ``ERRATA_A57_833471``: This applies errata 833471 workaround to Cortex-A57
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CPU. This needs to be enabled only for revision <= r1p2 of the CPU.
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- ``ERRATA_A57_859972``: This applies errata 859972 workaround to Cortex-A57
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CPU. This needs to be enabled only for revision <= r1p3 of the CPU.
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For Cortex-A72, the following errata build flags are defined :
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- ``ERRATA_A72_859971``: This applies errata 859971 workaround to Cortex-A72
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CPU. This needs to be enabled only for revision <= r0p3 of the CPU.
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For Cortex-A73, the following errata build flags are defined :
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- ``ERRATA_A73_852427``: This applies errata 852427 workaround to Cortex-A73
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CPU. This needs to be enabled only for revision r0p0 of the CPU.
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- ``ERRATA_A73_855423``: This applies errata 855423 workaround to Cortex-A73
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CPU. This needs to be enabled only for revision <= r0p1 of the CPU.
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For Cortex-A75, the following errata build flags are defined :
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- ``ERRATA_A75_764081``: This applies errata 764081 workaround to Cortex-A75
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CPU. This needs to be enabled only for revision r0p0 of the CPU.
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- ``ERRATA_A75_790748``: This applies errata 790748 workaround to Cortex-A75
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CPU. This needs to be enabled only for revision r0p0 of the CPU.
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For Cortex-A76, the following errata build flags are defined :
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- ``ERRATA_A76_1073348``: This applies errata 1073348 workaround to Cortex-A76
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CPU. This needs to be enabled only for revision <= r1p0 of the CPU.
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- ``ERRATA_A76_1130799``: This applies errata 1130799 workaround to Cortex-A76
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CPU. This needs to be enabled only for revision <= r2p0 of the CPU.
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- ``ERRATA_A76_1220197``: This applies errata 1220197 workaround to Cortex-A76
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CPU. This needs to be enabled only for revision <= r2p0 of the CPU.
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- ``ERRATA_A76_1257314``: This applies errata 1257314 workaround to Cortex-A76
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CPU. This needs to be enabled only for revision <= r3p0 of the CPU.
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- ``ERRATA_A76_1262606``: This applies errata 1262606 workaround to Cortex-A76
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CPU. This needs to be enabled only for revision <= r3p0 of the CPU.
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- ``ERRATA_A76_1262888``: This applies errata 1262888 workaround to Cortex-A76
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CPU. This needs to be enabled only for revision <= r3p0 of the CPU.
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- ``ERRATA_A76_1275112``: This applies errata 1275112 workaround to Cortex-A76
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CPU. This needs to be enabled only for revision <= r3p0 of the CPU.
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For Neoverse N1, the following errata build flags are defined :
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- ``ERRATA_N1_1073348``: This applies errata 1073348 workaround to Neoverse-N1
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CPU. This needs to be enabled only for revision r0p0 and r1p0 of the CPU.
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- ``ERRATA_N1_1130799``: This applies errata 1130799 workaround to Neoverse-N1
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CPU. This needs to be enabled only for revision <= r2p0 of the CPU.
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- ``ERRATA_N1_1165347``: This applies errata 1165347 workaround to Neoverse-N1
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CPU. This needs to be enabled only for revision <= r2p0 of the CPU.
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- ``ERRATA_N1_1207823``: This applies errata 1207823 workaround to Neoverse-N1
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CPU. This needs to be enabled only for revision <= r2p0 of the CPU.
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- ``ERRATA_N1_1220197``: This applies errata 1220197 workaround to Neoverse-N1
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CPU. This needs to be enabled only for revision <= r2p0 of the CPU.
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- ``ERRATA_N1_1257314``: This applies errata 1257314 workaround to Neoverse-N1
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CPU. This needs to be enabled only for revision <= r3p0 of the CPU.
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- ``ERRATA_N1_1262606``: This applies errata 1262606 workaround to Neoverse-N1
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CPU. This needs to be enabled only for revision <= r3p0 of the CPU.
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- ``ERRATA_N1_1262888``: This applies errata 1262888 workaround to Neoverse-N1
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CPU. This needs to be enabled only for revision <= r3p0 of the CPU.
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- ``ERRATA_N1_1275112``: This applies errata 1275112 workaround to Neoverse-N1
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CPU. This needs to be enabled only for revision <= r3p0 of the CPU.
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- ``ERRATA_N1_1315703``: This applies errata 1315703 workaround to Neoverse-N1
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CPU. This needs to be enabled only for revision <= r3p0 of the CPU.
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DSU Errata Workarounds
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----------------------
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Similar to CPU errata, TF-A also implements workarounds for DSU (DynamIQ
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Shared Unit) errata. The DSU errata details can be found in the respective Arm
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documentation:
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- `Arm DSU Software Developers Errata Notice`_.
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Each erratum is identified by an ``ID``, as defined in the DSU errata notice
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document. Thus, the build flags which enable/disable the errata workarounds
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have the format ``ERRATA_DSU_<ID>``. The implementation and application logic
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of DSU errata workarounds are similar to `CPU errata workarounds`_.
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For DSU errata, the following build flags are defined:
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- ``ERRATA_DSU_798953``: This applies errata 798953 workaround for the
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affected DSU configurations. This errata applies only for those DSUs that
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revision is r0p0 (on r0p1 it is fixed). However, please note that this
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workaround results in increased DSU power consumption on idle.
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- ``ERRATA_DSU_936184``: This applies errata 936184 workaround for the
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affected DSU configurations. This errata applies only for those DSUs that
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contain the ACP interface **and** the DSU revision is older than r2p0 (on
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r2p0 it is fixed). However, please note that this workaround results in
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increased DSU power consumption on idle.
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CPU Specific optimizations
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--------------------------
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This section describes some of the optimizations allowed by the CPU micro
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architecture that can be enabled by the platform as desired.
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- ``SKIP_A57_L1_FLUSH_PWR_DWN``: This flag enables an optimization in the
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Cortex-A57 cluster power down sequence by not flushing the Level 1 data
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cache. The L1 data cache and the L2 unified cache are inclusive. A flush
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of the L2 by set/way flushes any dirty lines from the L1 as well. This
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is a known safe deviation from the Cortex-A57 TRM defined power down
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sequence. Each Cortex-A57 based platform must make its own decision on
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whether to use the optimization.
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- ``A53_DISABLE_NON_TEMPORAL_HINT``: This flag disables the cache non-temporal
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hint. The LDNP/STNP instructions as implemented on Cortex-A53 do not behave
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in a way most programmers expect, and will most probably result in a
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significant speed degradation to any code that employs them. The Armv8-A
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architecture (see Arm DDI 0487A.h, section D3.4.3) allows cores to ignore
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the non-temporal hint and treat LDNP/STNP as LDP/STP instead. Enabling this
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flag enforces this behaviour. This needs to be enabled only for revisions
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<= r0p3 of the CPU and is enabled by default.
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- ``A57_DISABLE_NON_TEMPORAL_HINT``: This flag has the same behaviour as
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``A53_DISABLE_NON_TEMPORAL_HINT`` but for Cortex-A57. This needs to be
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enabled only for revisions <= r1p2 of the CPU and is enabled by default,
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as recommended in section "4.7 Non-Temporal Loads/Stores" of the
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`Cortex-A57 Software Optimization Guide`_.
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--------------
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*Copyright (c) 2014-2019, Arm Limited and Contributors. All rights reserved.*
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.. _CVE-2017-5715: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5715
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.. _CVE-2018-3639: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-3639
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.. _Cortex-A53 MPCore Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm048406/index.html
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.. _Cortex-A57 MPCore Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm049219/index.html
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.. _Cortex-A72 MPCore Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm012079/index.html
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.. _Firmware Design guide: firmware-design.rst
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.. _Cortex-A57 Software Optimization Guide: http://infocenter.arm.com/help/topic/com.arm.doc.uan0015b/Cortex_A57_Software_Optimization_Guide_external.pdf
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.. _Arm DSU Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm138168/index.html
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