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>
c51f73f77f