performance issues.
* Access to the GPIO bus is already locked by requesting
and releasing the bus - thus the lock isn't really needed
for each GPIO pin change.
* Don't lock and unlock the GPIO bus for -each- i2c access -
the i2c bus code is already doing this by calling the upper
layer callback to request/release the bus. This thus locks
the bus for the entirety of the transaction.
TODO:
* Further verify that everything is correctly requesting/
releasing the GPIO bus.
* Look at how to lock the GPIO pin configuration stuff,
potentially by locking/unlocking the bus at the gpiobus
layer.
config and function mask setup.
* "gpiomask" now specifies which GPIO pins to enable, for devices to bind to.
* "function_set" allows bits in the function register to be set at GPIO setup.
* "function_clear" allows bits in the function register to be cleared at
GPIO setup.
The function_set/function_clear bits allow for individual GPIO pins to either
drive a GPIO line or an alternate function - eg USB, JTAG, etc. This allows
for things like CS1/CS2 be enabled for those boards w/ >1 SPI device connected,
or disabling JTAG for the AR7240 (which is apparently needed ..)
I've verified this on the AR71xx.
