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.
It is the backport of linux commit ede033e1e863c ('dt-bindings:
gpio: document the new pull-up/pull-down flags')
from Thomas Petazzoni <thomas.petazzoni@bootlin.com>
and integrated in v5.1-rc1
https://github.com/torvalds/linux/commit/ede033e1e863c
Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/device-tree-bindings/gpio/gpio.txt b/doc/device-tree-bindings/gpio/gpio.txt
index e146917..e9ef021 100644
--- a/doc/device-tree-bindings/gpio/gpio.txt
+++ b/doc/device-tree-bindings/gpio/gpio.txt
@@ -65,6 +65,30 @@
GPIO_ACTIVE_HIGH is 0, so in this example gpio-specifier is "18 0" and encodes
GPIO pin number, and GPIO flags as accepted by the "qe_pio_e" gpio-controller.
+Optional standard bitfield specifiers for the last cell:
+
+- Bit 0: 0 means active high, 1 means active low
+- Bit 1: 0 mean push-pull wiring, see:
+ https://en.wikipedia.org/wiki/Push-pull_output
+ 1 means single-ended wiring, see:
+ https://en.wikipedia.org/wiki/Single-ended_triode
+- Bit 2: 0 means open-source, 1 means open drain, see:
+ https://en.wikipedia.org/wiki/Open_collector
+- Bit 3: 0 means the output should be maintained during sleep/low-power mode
+ 1 means the output state can be lost during sleep/low-power mode
+- Bit 4: 0 means no pull-up resistor should be enabled
+ 1 means a pull-up resistor should be enabled
+ This setting only applies to hardware with a simple on/off
+ control for pull-up configuration. If the hardware has more
+ elaborate pull-up configuration, it should be represented
+ using a pin control binding.
+- Bit 5: 0 means no pull-down resistor should be enabled
+ 1 means a pull-down resistor should be enabled
+ This setting only applies to hardware with a simple on/off
+ control for pull-down configuration. If the hardware has more
+ elaborate pull-down configuration, it should be represented
+ using a pin control binding.
+
1.1) GPIO specifier best practices
----------------------------------
diff --git a/include/dt-bindings/gpio/gpio.h b/include/dt-bindings/gpio/gpio.h
index 2cc10ae..c029467 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