This adds a ramp-up delay (in us) for adding a delay after enabling
GPIO. This is necessary if the ramp-up time is increased by some external
components. Usually this is quite fast, but certain combinations can
increase this to grater than 100ms.
Signed-off-by: Alexander Stein <alexander.stein@xxxxxxxxxxxxxxx>
---
.../devicetree/bindings/gpio/gpio.txt | 22 +++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt
index 5663e71b751fc..b87669dce9a61 100644
--- a/Documentation/devicetree/bindings/gpio/gpio.txt
+++ b/Documentation/devicetree/bindings/gpio/gpio.txt
@@ -182,6 +182,28 @@ gpio-controller@00000000 {
"poweroff", "reset";
}
+Optionally, a GPIO controller may have a "gpio-ramp-up-delays-us" property.
+This is an array of u32 defining the ramp-up delays of the GPIO lines
+going out of the GPIO controller. This might be necessary if external
+components (e.g. capacitors, resistors) increase the ramp up time notably.
+The delay are assigned starting from line offset 0 from
+left to right from the passed array. An incomplete array (where the number
+of passed delays are less than ngpios) will still be used up until the last
+provided valid line index. Setting to will not add any delay.
+
+Example:
+
+gpio-controller@00000000 {
+ compatible = "foo";
+ reg = <0x00000000 0x1000>;
+ gpio-controller;
+ #gpio-cells = <2>;
+ gpio-ramp-up-delays-us = <0>, <0>, <0>, <0>,
+ <0>, <0>, <120000>, <0>,
+ <0>, <0>, <0>, <0>,
+ <0>, <0>, <0>, <0>;
+}
+
The GPIO chip may contain GPIO hog definitions. GPIO hogging is a mechanism
providing automatic GPIO request and configuration as part of the
gpio-controller's driver probe function.
--
2.34.1
