There are cases where a certain default output value in the 74x164
output is needed.
For example: the imx6ul-evk board has the Ethernet PHY reset controlled
by the 74x164 chip.
After enabling the OE pin, the output pins of the 74x164 chip go to
zero by default, which makes the Ethernet PHY not to be detected.
Add a new optional property called 'registers-default' that allows
describing the default output value for each shift register.
Signed-off-by: Fabio Estevam <festevam@xxxxxxxxx>
---
Changes since v1:
- None
Documentation/devicetree/bindings/gpio/gpio-74x164.txt | 3 +++
1 file changed, 3 insertions(+)
diff --git a/Documentation/devicetree/bindings/gpio/gpio-74x164.txt b/Documentation/devicetree/bindings/gpio/gpio-74x164.txt
index 2a97553d8d76..bf8f45896018 100644
--- a/Documentation/devicetree/bindings/gpio/gpio-74x164.txt
+++ b/Documentation/devicetree/bindings/gpio/gpio-74x164.txt
@@ -14,6 +14,8 @@ Required properties:
Optional properties:
- enable-gpios: GPIO connected to the OE (Output Enable) pin.
+- registers-default: An array of 8-bit values describing the default output
+value of each shift registers.
Example:
@@ -24,4 +26,5 @@ gpio5: gpio5@0 {
#gpio-cells = <2>;
registers-number = <4>;
spi-max-frequency = <100000>;
+ registers-default = /bits/ 8 <0x57 0xF0 0xFF 0xF0>;
};
--
2.17.1
