configure the mux and config registers for PIO devices based on what
we find in the FDT. I developed it per the spec that had been
committed to Linux in the January 2014 time frame and haven't
updated. In short, bundles of pins are activated in specific ways for
specific configurations, and we implement all of that.
What's not included is a MI device infrastructure, any dynamic
run-time changing of these pins, etc. Also not included are hooks into
all the drivers to enable the latter (static at boot no driver changes
are needed). These larger questions will need to be answered once we
have more drivers like this for more platforms, or somebody has a heck
of a lot of time to research a bunch of platforms, the Linux solution
(which is good, but has its warts), etc.
add the ability for userland to be notified of changes on gpio pins via
a select(2)/read(2) interface.
Change the interrupt handler from filtered to threaded.
Because of the uiomove() calls in the new interface, change locking from
standard mutex to sx.
Add / restore the at91_gpio_high_z() function.
Reviewed by: imp (long ago)
Introduce framework to configure the multiplexed pins on boot.
Since the USART supprots RS-485 multidrop mode, it allows the
TX pins to float. However, for RS-232 operations, we don't
want these pins to float. Instead, they should be pulled up
to avoid mismatches. Linux does something similar when it
configures the TX lines. This implies that we also allow the
RX lines to float rather than be in the state they are left in
by the boot loader. Since they are input pins, I think that
this is the right thing to do.
Plus minor for our board.
