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Diffstat (limited to 'docs/cpu-specific-build-macros.md')
| -rw-r--r-- | docs/cpu-specific-build-macros.md | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/docs/cpu-specific-build-macros.md b/docs/cpu-specific-build-macros.md index d9b7108c..c57dc7ee 100644 --- a/docs/cpu-specific-build-macros.md +++ b/docs/cpu-specific-build-macros.md @@ -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 +74,23 @@ 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, + as recommended in section "4.7 Non-Temporal Loads/Stores" of the + [Cortex-A57 Software Optimization Guide][A57 SW Optimization Guide]. + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -_Copyright (c) 2014, ARM Limited and Contributors. All rights reserved._ +_Copyright (c) 2014-2016, ARM Limited and Contributors. All rights reserved._ + +[A57 SW Optimization Guide]: http://infocenter.arm.com/help/topic/com.arm.doc.uan0015b/Cortex_A57_Software_Optimization_Guide_external.pdf |