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authorThomas Petazzoni <thomas.petazzoni@bootlin.com>2019-02-07 17:28:55 +0100
committerLinus Walleij <linus.walleij@linaro.org>2019-02-13 09:07:43 +0100
commitede033e1e863c36729de25b57145fff287415830 (patch)
tree51113627e623b97fcb8f647dd06431b316cc5ceb /include/dt-bindings
parentbfeffd155283772bbe78c6a05dec7c0128ee500c (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.h6
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