• Thomas Petazzoni's avatar
    dt-bindings: gpio: document the new pull-up/pull-down flags · ede033e1
    Thomas Petazzoni authored
    This commit extends the flags that can be used in GPIO specifiers to
    indicate if a pull-up resistor or pull-down resistor should be
    enabled.
    
    While some pinctrl DT bindings already offer the capability of
    configuring pull-up/pull-down resistors at the pin level, a number of
    simple GPIO controllers don't have any pinmuxing capability, and
    therefore do not rely on the pinctrl DT bindings.
    
    Such simple GPIO controllers however sometimes allow to configure
    pull-up and pull-down resistors on a per-pin basis, and whether such
    resistors should be enabled or not is a highly board-specific HW
    characteristic.
    
    By using two additional bits of the GPIO flag specifier, we can easily
    allow the Device Tree to describe which GPIOs should have their
    pull-up or pull-down resistors enabled. Even though the two options
    are mutually exclusive, we still need two bits to encode at least
    three states: no pull-up/pull-down, pull-up, pull-down.
    Signed-off-by: default avatarThomas Petazzoni <thomas.petazzoni@bootlin.com>
    Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
    ede033e1
gpio.txt 13.1 KB