mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-11-24 21:54:01 +00:00
00275f5ead
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>
50 lines
1.8 KiB
ReStructuredText
50 lines
1.8 KiB
ReStructuredText
.. 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.
|