Add an example using the RTC to help with a lower power design. This is
a sister example to the existing "button-irq-printf", which is
functionally identical, but uses far less power.
There's more tricks that can be done to lower the power even further,
but this shows a few of the early steps that can be done, using the RTC
wakeup instead of a timer.
Code added for L1 to support the PWR Control block didn't properly
follow the HACKING_COMMON_DOC guidelines. The naming was wrong, and
some headers were missing. This commit has no functional changes, it
only addresses the style and structure problems.
Earlier additions to the L1 support were not correctly using linux
coding guidelines as specified in /HACKING.
Some examples were also missing license information.
Despite the L1 being a low power device, my initial focus is on making
it basically compatible with existing devices.
To that end, provide clock setup helper routines that configure it for maximum performance,
allowing some similar clock speeds to F1 devices to help with testing. This requires adding
the power chipset routines to set the voltage range.
Clock setup style is similar to the F4 code, which seems nicer than the overflow of different
routines used on the F1 code.
NOTE: Both the F4 existing pwr code, and this code don't actually include the f1 core power
code, even though it should be compatible
