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author | Stefan Roese <sr@denx.de> | 2022-09-02 14:57:53 +0300 |
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committer | Tom Rini <trini@konsulko.com> | 2022-09-13 23:01:44 +0300 |
commit | 00275f5ead89dcbed583da2a698b7ba2c6384d0d (patch) | |
tree | da5befb3e8b8c5fcfacd4854c36ae73c8912b998 /doc/develop | |
parent | 5ee0fa722c300d443b82d214a67583b36ae40909 (diff) | |
download | u-boot-00275f5ead89dcbed583da2a698b7ba2c6384d0d.tar.xz |
cyclic: Add documentation
Add documentation for the cyclic function infrastructure, including the
cyclic command.
Signed-off-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Diffstat (limited to 'doc/develop')
-rw-r--r-- | doc/develop/cyclic.rst | 50 | ||||
-rw-r--r-- | doc/develop/index.rst | 1 |
2 files changed, 51 insertions, 0 deletions
diff --git a/doc/develop/cyclic.rst b/doc/develop/cyclic.rst new file mode 100644 index 0000000000..43bedacb9f --- /dev/null +++ b/doc/develop/cyclic.rst @@ -0,0 +1,50 @@ +.. SPDX-License-Identifier: GPL-2.0+ + +Cyclic functions +================ + +The cyclic function execution infrastruture provides a way to periodically +execute code, e.g. every 100ms. Examples for such functions might be LED +blinking etc. The functions that are hooked into this cyclic list should +be small timewise as otherwise the execution of the other code that relies +on a high frequent polling (e.g. UART rx char ready check) might be +delayed too much. To detect cyclic functions with a too long execution +time, the Kconfig option `CONFIG_CYCLIC_MAX_CPU_TIME_US` is introduced, +which configures the max allowed time for such a cyclic function. If it's +execution time exceeds this time, this cyclic function will get removed +from the cyclic list. + +Registering a cyclic function +----------------------------- + +To register a cyclic function, use something like this:: + + static void cyclic_demo(void *ctx) + { + /* Just a small dummy delay here */ + udelay(10); + } + + int board_init(void) + { + struct cyclic_info *cyclic; + + /* Register demo cyclic function */ + cyclic = cyclic_register(cyclic_demo, 10 * 1000, "cyclic_demo", NULL); + if (!cyclic) + printf("Registering of cyclic_demo failed\n"); + + return 0; + } + +This will register the function `cyclic_demo()` to be periodically +executed all 10ms. + +How is this cyclic functionality integrated / executed? +-------------------------------------------------------- + +The cyclic infrastructure integrates the main function responsible for +calling all registered cyclic functions cyclic_run() into the common +WATCHDOG_RESET macro. This guarantees that cyclic_run() is executed +very often, which is necessary for the cyclic functions to get scheduled +and executed at their configured periods. diff --git a/doc/develop/index.rst b/doc/develop/index.rst index f7ee09db24..ce6b38e576 100644 --- a/doc/develop/index.rst +++ b/doc/develop/index.rst @@ -27,6 +27,7 @@ Implementation ci_testing commands config_binding + cyclic devicetree/index distro driver-model/index |