diff options
author | Jeenu Viswambharan <jeenu.viswambharan@arm.com> | 2017-01-16 16:52:35 +0000 |
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committer | Jeenu Viswambharan <jeenu.viswambharan@arm.com> | 2017-02-14 09:26:11 +0000 |
commit | c877b414870bb3e421518caf9c7652a9807419b5 (patch) | |
tree | f7d2837cb46edd4f3578d39985c4d13fa97e419d /docs | |
parent | 4d07e7821e19dc1ebc640f5264c2a769354c8b2d (diff) |
Introduce locking primitives using CAS instruction
The ARMv8v.1 architecture extension has introduced support for far
atomics, which includes compare-and-swap. Compare and Swap instruction
is only available for AArch64.
Introduce build options to choose the architecture versions to target
ARM Trusted Firmware:
- ARM_ARCH_MAJOR: selects the major version of target ARM
Architecture. Default value is 8.
- ARM_ARCH_MINOR: selects the minor version of target ARM
Architecture. Default value is 0.
When:
(ARM_ARCH_MAJOR > 8) || ((ARM_ARCH_MAJOR == 8) && (ARM_ARCH_MINOR >= 1)),
for AArch64, Compare and Swap instruction is used to implement spin
locks. Otherwise, the implementation falls back to using
load-/store-exclusive instructions.
Update user guide, and introduce a section in Firmware Design guide to
summarize support for features introduced in ARMv8 Architecture
Extensions.
Change-Id: I73096a0039502f7aef9ec6ab3ae36680da033f16
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
Diffstat (limited to 'docs')
-rw-r--r-- | docs/firmware-design.md | 41 | ||||
-rw-r--r-- | docs/user-guide.md | 8 |
2 files changed, 45 insertions, 4 deletions
diff --git a/docs/firmware-design.md b/docs/firmware-design.md index bd6e2f69..0fdc941c 100644 --- a/docs/firmware-design.md +++ b/docs/firmware-design.md @@ -16,8 +16,9 @@ Contents : 11. [Use of coherent memory in Trusted Firmware](#11--use-of-coherent-memory-in-trusted-firmware) 12. [Isolating code and read-only data on separate memory pages](#12--isolating-code-and-read-only-data-on-separate-memory-pages) 13. [Performance Measurement Framework](#13--performance-measurement-framework) -14. [Code Structure](#14--code-structure) -15. [References](#15--references) +14. [ARMv8 Architecture Extensions](#14--armv8-architecture-extensions) +15. [Code Structure](#15--code-structure) +16. [References](#16--references) 1. Introduction @@ -2208,7 +2209,39 @@ in this implementation. 5. `pmf_helpers.h` is an internal header used by `pmf.h`. -14. Code Structure +14. ARMv8 Architecture Extensions +---------------------------------- + +ARM Trusted Firmware makes use of ARMv8 Architecture Extensions where +applicable. This section lists the usage of Architecture Extensions, and build +flags controlling them. + +In general, and unless individually mentioned, the build options +`ARM_ARCH_MAJOR` and `ARM_ARCH_MINOR` selects the Architecture Extension to +target when building ARM Trusted Firmware. Subsequent ARM Architecture +Extensions are backward compatible with previous versions. + +The build system only requires that `ARM_ARCH_MAJOR` and `ARM_ARCH_MINOR` have a +valid numeric value. These build options only control whether or not +Architecture Extension-specific code is included in the build. Otherwise, ARM +Trusted Firmware targets the base ARMv8.0 architecture; i.e. as if +`ARM_ARCH_MAJOR` == 8 and `ARM_ARCH_MINOR` == 0, which are also their respective +default values. + +See also the _Summary of build options_ in [User Guide]. + +For details on the Architecture Extension and available features, please refer +to the respective Architecture Extension Supplement. + +### ARMv8.1 + +This Architecture Extension is targeted when `ARM_ARCH_MAJOR` >= 8, or when +`ARM_ARCH_MAJOR` == 8 and `ARM_ARCH_MINOR` >= 1. + +* The Compare and Swap instruction is used to implement spinlocks. Otherwise, + the load-/store-exclusive instruction pair is used. + +15. Code Structure ------------------- Trusted Firmware code is logically divided between the three boot loader @@ -2252,7 +2285,7 @@ FDTs provide a description of the hardware platform and are used by the Linux kernel at boot time. These can be found in the `fdts` directory. -15. References +16. References --------------- 1. Trusted Board Boot Requirements CLIENT PDD (ARM DEN 0006B-5). Available diff --git a/docs/user-guide.md b/docs/user-guide.md index c68565b7..7ae5b9ce 100644 --- a/docs/user-guide.md +++ b/docs/user-guide.md @@ -181,6 +181,14 @@ performed. is used to determine the number of valid slave interfaces available in the ARM CCI driver. Default is 400 (that is, CCI-400). +* `ARM_ARCH_MAJOR`: The major version of ARM Architecture to target when + compiling ARM Trusted Firmware. Its value must be numeric, and defaults to + 8. See also, _ARMv8 Architecture Extensions_ in [Firmware Design]. + +* `ARM_ARCH_MINOR`: The minor version of ARM Architecture to target when + compiling ARM Trusted Firmware. Its value must be a numeric, and defaults + to 0. See also, _ARMv8 Architecture Extensions_ in [Firmware Design]. + * `ARM_GIC_ARCH`: Choice of ARM GIC architecture version used by the ARM Legacy GIC driver for implementing the platform GIC API. This API is used by the interrupt management framework. Default is 2 (that is, version 2.0). |