1.. _cache_config:
2
3Cache Control Configuration
4###########################
5
6This is a high-level guide to Zephyr's cache interface and Kconfig options related to
7cache controllers. See :ref:`cache_api` for API reference material.
8
9Zephyr has different Kconfig options to control how the cache controller is
10implemented and controlled.
11
12* :kconfig:option:`CONFIG_CPU_HAS_DCACHE` /
13  :kconfig:option:`CONFIG_CPU_HAS_ICACHE`: these hidden options should be
14  selected at SoC / platform level when the CPU actually supports a data or
15  instruction cache. The cache controller can be in the core or can be an
16  external cache controller for which a driver is provided.
17
18  These options have the goal to document an available hardware feature and
19  should be set whether we plan to support and use the cache control in Zephyr
20  or not.
21
22* :kconfig:option:`CONFIG_DCACHE` / :kconfig:option:`CONFIG_ICACHE`: these
23  options must be selected when support for data or instruction cache is
24  present and working in zephyr. Note that if these options are disabled,
25  caching may still be enabled depending on the hardware defaults.
26
27  All the code paths related to cache control must be conditionally enabled
28  depending on these symbols. When the symbol is set the cache is considered
29  enabled and used.
30
31  These symbols say nothing about the actual API interface exposed to the user.
32  For example a platform using the data cache can enable the
33  :kconfig:option:`CONFIG_DCACHE` symbol and use some HAL exported function in
34  some platform-specific code to enable and manage the d-cache.
35
36* :kconfig:option:`CONFIG_CACHE_MANAGEMENT`: this option must be selected when
37  the cache operations are exposed to the user through a standard API (see
38  :ref:`cache_api`).
39
40  When this option is enabled we assume that all the cache functions are
41  implemented in the architectural code or in an external cache controller
42  driver.
43
44* :kconfig:option:`CONFIG_MEM_ATTR`: this option allows the user to
45  specify (using :ref:`memory region attributes<mem_mgmt_api>`) a fixed region
46  in memory that will have caching disabled once the kernel has initialized.
47
48* :kconfig:option:`CONFIG_NOCACHE_MEMORY`: this option allows the user to
49  specify individual global variables as uncached using ``__nocache``. This will
50  instruct the linker to place any marked variables into a special ``nocache``
51  region in memory and the MPU driver will configure that region as uncached.
52
53* :kconfig:option:`CONFIG_ARCH_CACHE`/:kconfig:option:`CONFIG_EXTERNAL_CACHE`:
54  mutually exclusive options for :kconfig:option:`CACHE_TYPE` used to define
55  whether the cache operations are implemented at arch level or using an
56  external cache controller with a provided driver.
57
58  * :kconfig:option:`CONFIG_ARCH_CACHE`: the cache API is implemented by the
59    arch code
60
61  * :kconfig:option:`CONFIG_EXTERNAL_CACHE`: the cache API is implemented by a
62    driver that supports the external cache controller. In this case the driver
63    must be located as usual in the :file:`drivers/cache/` directory
64
65.. _cache_api:
66
67Cache API
68#########
69
70.. doxygengroup:: cache_interface
71