diff options
| author | Thomas Petazzoni <thomas.petazzoni@bootlin.com> | 2019-02-07 17:28:55 +0100 |
|---|---|---|
| committer | Linus Walleij <linus.walleij@linaro.org> | 2019-02-13 09:07:43 +0100 |
| commit | ede033e1e863c36729de25b57145fff287415830 (patch) | |
| tree | 51113627e623b97fcb8f647dd06431b316cc5ceb /include/dt-bindings | |
| parent | bfeffd155283772bbe78c6a05dec7c0128ee500c (diff) | |
dt-bindings: gpio: document the new pull-up/pull-down flags
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: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'include/dt-bindings')
| -rw-r--r-- | include/dt-bindings/gpio/gpio.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/include/dt-bindings/gpio/gpio.h b/include/dt-bindings/gpio/gpio.h index 2cc10ae4bbb7..c029467e828b 100644 --- a/include/dt-bindings/gpio/gpio.h +++ b/include/dt-bindings/gpio/gpio.h @@ -33,4 +33,10 @@ #define GPIO_PERSISTENT 0 #define GPIO_TRANSITORY 8 +/* Bit 4 express pull up */ +#define GPIO_PULL_UP 16 + +/* Bit 5 express pull down */ +#define GPIO_PULL_DOWN 32 + #endif |