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boot: add CONFIG_BOOT_DELAY option

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Introduce a configurable boot delay option (defaulting to none) that
happens right after printing a boot delay banner, #before calling
main() in kernel/init.c:_main(), before taking timestamps for _main()
and once all the infrastructure is in place. Move also the boot banner
to happen after this delay.

The rationale for this is some boards will boot really fast and print
out some test case output in the serial port before the system that is
monitoring the serial port is able to read from the serial port.

This happens in MCUs whose serial port is embedded in a USB connection
which also is used to power the MCU board. When powering it on by
powering the USB port, there is a time it takes the host system to
detect the USB connection, enumerate the serial port, configure it and
load, start and read from the serial port. At this time, it might have
printed the output of the serial port.

While manually it is possible to press a reset button, on automation
setups this adds a lot of overhead and cabling or modifications to the
MCU that are easier (and cheaper) to overcome with this delay. Other
options (like using a separate serial line) might not be possible or
add a lot of cabling and cost, plus it'd also add extra build
configuration.

Change-Id: I2f4d1ba356de6cefa19b4ef5c9f19f87885d4dfd
Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
This commit is contained in:
Inaky Perez-Gonzalez 2017-06-20 17:01:09 -07:00 • committed by Anas Nashif
commit c51f73f77f
2 changed files with 32 additions and 3 deletions
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14
kernel/Kconfig
View file

@ -204,6 +204,20 @@ config BOOT_BANNER
This option outputs a banner to the console device during boot up. It
also embeds a date & time stamp in the kernel and in each USAP image.
config BOOT_DELAY
int "milliseconds to delay boot"
prompt "Boot delay"
default 0
help
This option delays bootup for the specified amount of
milliseconds. This is used to allow serial ports to get ready
before starting to print information on them during boot, as
some systems might boot to fast for a receiving endpoint to
detect the new USB serial bus, enumerate it and get ready to
receive before it actually gets data. A similar effect can be
achieved by waiting for DCD on the serial port--however, not
all serial ports have DCD.
config BUILD_TIMESTAMP
bool
prompt "Build Timestamp"

21
kernel/init.c
View file

@ -37,7 +37,17 @@ const char * const build_timestamp = BUILD_TIMESTAMP;
/* boot banner items */
#define BOOT_BANNER "BOOTING ZEPHYR OS v" KERNEL_VERSION_STRING
static const unsigned int boot_delay;
#if defined(CONFIG_BOOT_DELAY) && CONFIG_BOOT_DELAY > 0
#define BOOT_DELAY_BANNER " (delayed boot " \
STRINGIFY(CONFIG_BOOT_DELAY) "ms)"
static const unsigned int boot_delay = CONFIG_BOOT_DELAY;
#else
#define BOOT_DELAY_BANNER ""
static const unsigned int boot_delay;
#endif
#define BOOT_BANNER "BOOTING ZEPHYR OS v" \
KERNEL_VERSION_STRING BOOT_DELAY_BANNER
#if !defined(CONFIG_BOOT_BANNER)
#define PRINT_BOOT_BANNER() do { } while (0)
@ -200,6 +210,13 @@ static void _main(void *unused1, void *unused2, void *unused3)
_init_static_threads();
if (boot_delay > 0) {
printk("***** delaying boot " STRINGIFY(CONFIG_BOOT_DELAY)
"ms (per build configuration) *****\n");
k_sleep(CONFIG_BOOT_DELAY);
}
PRINT_BOOT_BANNER();
#ifdef CONFIG_BOOT_TIME_MEASUREMENT
/* record timestamp for kernel's _main() function */
extern u64_t __main_time_stamp;
@ -360,8 +377,6 @@ FUNC_NORETURN void _Cstart(void)
/* display boot banner */
PRINT_BOOT_BANNER();
switch_to_main_thread();
/*