9aba1323ce
Wrong levels and cache topic appearing in the wrong table of contents. Signed-off-by: Anas Nashif <anas.nashif@intel.com>
71 lines
3.1 KiB
ReStructuredText
71 lines
3.1 KiB
ReStructuredText
.. _cache_config:
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Cache Control Configuration
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###########################
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This is a high-level guide to Zephyr's cache interface and Kconfig options related to
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cache controllers. See :ref:`cache_api` for API reference material.
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Zephyr has different Kconfig options to control how the cache controller is
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implemented and controlled.
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* :kconfig:option:`CONFIG_CPU_HAS_DCACHE` /
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:kconfig:option:`CONFIG_CPU_HAS_ICACHE`: these hidden options should be
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selected at SoC / platform level when the CPU actually supports a data or
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instruction cache. The cache controller can be in the core or can be an
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external cache controller for which a driver is provided.
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These options have the goal to document an available hardware feature and
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should be set whether we plan to support and use the cache control in Zephyr
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or not.
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* :kconfig:option:`CONFIG_DCACHE` / :kconfig:option:`CONFIG_ICACHE`: these
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options must be selected when support for data or instruction cache is
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present and working in zephyr. Note that if these options are disabled,
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caching may still be enabled depending on the hardware defaults.
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All the code paths related to cache control must be conditionally enabled
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depending on these symbols. When the symbol is set the cache is considered
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enabled and used.
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These symbols say nothing about the actual API interface exposed to the user.
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For example a platform using the data cache can enable the
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:kconfig:option:`CONFIG_DCACHE` symbol and use some HAL exported function in
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some platform-specific code to enable and manage the d-cache.
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* :kconfig:option:`CONFIG_CACHE_MANAGEMENT`: this option must be selected when
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the cache operations are exposed to the user through a standard API (see
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:ref:`cache_api`).
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When this option is enabled we assume that all the cache functions are
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implemented in the architectural code or in an external cache controller
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driver.
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* :kconfig:option:`CONFIG_MEM_ATTR`: this option allows the user to
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specify (using :ref:`memory region attributes<mem_mgmt_api>`) a fixed region
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in memory that will have caching disabled once the kernel has initialized.
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* :kconfig:option:`CONFIG_NOCACHE_MEMORY`: this option allows the user to
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specify individual global variables as uncached using ``__nocache``. This will
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instruct the linker to place any marked variables into a special ``nocache``
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region in memory and the MPU driver will configure that region as uncached.
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* :kconfig:option:`CONFIG_ARCH_CACHE`/:kconfig:option:`CONFIG_EXTERNAL_CACHE`:
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mutually exclusive options for :kconfig:option:`CACHE_TYPE` used to define
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whether the cache operations are implemented at arch level or using an
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external cache controller with a provided driver.
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* :kconfig:option:`CONFIG_ARCH_CACHE`: the cache API is implemented by the
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arch code
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* :kconfig:option:`CONFIG_EXTERNAL_CACHE`: the cache API is implemented by a
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driver that supports the external cache controller. In this case the driver
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must be located as usual in the :file:`drivers/cache/` directory
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.. _cache_api:
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Cache API
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*********
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.. doxygengroup:: cache_interface
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