No new content, just correcting a few typographical errors. (From OE-Core rev: 8df13f5013d92954ee76943dad58db75704c3cc5) Signed-off-by: Darren Hart <dvhart@linux.intel.com> Cc: Richard Purdie <richard.purdie@linuxfoundation.org> Cc: Paul Eggleton <paul.eggleton@intel.com> Cc: Tom Zanussi <tom.zanussi@intel.com> Cc: Nitin Kamble <nitin.a.kamble@intel.com> Cc: Mark Hatle <mark.hatle@windriver.com> Cc: Bruce Ashfield <bruce.ashfield@windriver.com> Cc: Martin Jansa <martin.jansa@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
101 lines
4.6 KiB
Text
101 lines
4.6 KiB
Text
2012/03/30 - Mark Hatle <mark.hatle@windriver.com>
|
|
- Initial Revision
|
|
|
|
|
|
Introduction
|
|
============
|
|
The individual CPU, and ABI tunings are contained in this directory. A
|
|
number of local and global variables are used to control the way the
|
|
tunings are setup and how they work together to specify an optimized
|
|
configuration.
|
|
|
|
The following is brief summary of the generic components that are used
|
|
in these tunings.
|
|
|
|
AVAILTUNES - This is a list of all of the tuning definitions currently
|
|
available in the system. Not all tunes in this list may be compatible
|
|
with the machine configuration, or each other in a multilib
|
|
configuration. Each tuning file can add to this list using "+=", but
|
|
should never replace the list using "=".
|
|
|
|
DEFAULTTUNE - This specifies the tune to use for a particular build.
|
|
Each tune should specify a reasonable default, which can be overriden by
|
|
a machine or multilib configuration. The specified tune must be listed
|
|
in the AVAILTUNES.
|
|
|
|
TUNEVALID[feature] - The <feature> is defined with a human readable
|
|
explanation for what it does. All architectural, cpu, abi, etc tuning
|
|
features must be defined using TUNEVALID.
|
|
|
|
TUNECONFLICTS[feature] - A list of features which conflict with <feature>.
|
|
New sanity checks will try to reject combinations in which a single
|
|
tuning ends up with features which conflict with each other.
|
|
|
|
TUNE_FEATURES - This is automatically defined as TUNE_FEATURES_tune-<tune>.
|
|
See TUNE_FEATURES_tune-<tune> for more information.
|
|
|
|
TUNE_FEATURES_tune-<tune> - Specify the features used to describe a
|
|
specific tune. This is a list of features that a tune support, each
|
|
feature must be in the TUNEVALID list. Note: the tune and a given
|
|
feature name may be the same, but they have different purposes. Only
|
|
features may be used to change behavior, while tunes are used to
|
|
describe an overall set of features.
|
|
|
|
ABIEXTENSION - An ABI extension may be specified by a specific feature
|
|
or other tuning setting, such as TARGET_FPU. Any ABI extensions either
|
|
need to be defined in the architectures base arch file, i.e.
|
|
ABIEXTENSION = "eabi" in the arm case, or appended to in specific tune
|
|
files with a ".=". Spaces are not allowed in this variable.
|
|
|
|
TUNE_CCARGS - Setup the cflags based on the TUNE_FEATURES settings.
|
|
These should be additive when defined using "+=". All items in this
|
|
list should be dynamic! i.e.
|
|
${@bb.utils.contains("TUNE_FEATURES", "feature", "cflag", "!cflag", d)}
|
|
|
|
TUNE_ARCH - The GNU canonical arch for a specific architecture. i.e.
|
|
arm, armeb, mips, mips64, etc. This value is used by bitbake to setup
|
|
configure. TUNE_ARCH definitions are specific to a given architecture.
|
|
They may be a single static definition, or may be dynamically adjusted.
|
|
See each architecture's README for details for that CPU family.
|
|
|
|
TUNE_PKGARCH - The package architecture used by the packaging systems to
|
|
define the architecture, abi and tuning of a particular package.
|
|
Similarly to TUNE_ARCH, the definition of TUNE_PKGARCH is specific to
|
|
each architecture. See each architectures README for details for that
|
|
CPU family.
|
|
|
|
PACKAGE_EXTRA_ARCHS - Lists all runtime compatible package
|
|
architectures. By default this is equal to
|
|
PACKAGE_EXTRA_ARCHS_tune-<tune>. If an architecture deviates from the
|
|
default it will be listed in the architecture README.
|
|
|
|
PACKAGE_EXTRA_ARCHS_tune-<tune> - List all of the package architectures
|
|
that are compatible with this specific tune. The package arch of this
|
|
tune must be in the list.
|
|
|
|
TARGET_FPU - The FPU setting for a given tune, hard (generate floating
|
|
point instructions), soft (generate internal gcc calls), "other"
|
|
architecture specific floating point. This is synchronized with the
|
|
compiler and other toolchain items. This should be dynamically
|
|
configured in the same way that TUNE_CCARGS is.
|
|
|
|
BASE_LIB_tune-<tune> - The "/lib" location for a specific ABI. This is
|
|
used in a multilib configuration to place the libraries in the correct,
|
|
non-conflicting locations.
|
|
|
|
|
|
Best Practice
|
|
=============
|
|
The tune infrastructure is designed to be hierarchical. When writing a
|
|
new tune file for a "fast-forward" CPU architecture (one that supports
|
|
everything from a previous generation), it is recommended to require the
|
|
previous generation tune file and specify PACKAGE_EXTRA_ARCHS using the
|
|
previous generation's override and appending the new tune. Note that
|
|
only one previous tune file should be included to avoid mutiple includes
|
|
of the base arch which could lead to a broken configuration due to
|
|
multiple prepend and append assignments.
|
|
|
|
For example, for x86, there is a common x86/arch-x86.inc which is
|
|
included in the base i586 tune file. The core2 tune builds
|
|
on that, and corei7 builds on core2.
|