overlays: Add a pull (up/down) parameter to pps-gpio

Square wave output from RTCs such as the DS3231 requires a pullup
resistor. This commit allows the pin's internal pull resistors to be
used by specifying "pull=up" or "pull=down" as necessary.

diff --git a/arch/arm/boot/dts/overlays/README b/arch/arm/boot/dts/overlays/README
index 3152c23..f958481 100644 (file)
--- a/arch/arm/boot/dts/overlays/README
+++ b/arch/arm/boot/dts/overlays/README
@@ -3102,6 +3102,8 @@ Params: gpiopin                 Input GPIO (default "18")
                                 off)
         capture_clear           Generate clear events on the trailing edge
                                 (default off)
+        pull                    Desired pull-up/down state (off, down, up)
+                                Default is "off".
 
 
 Name:   pwm

diff --git a/arch/arm/boot/dts/overlays/pps-gpio-overlay.dts b/arch/arm/boot/dts/overlays/pps-gpio-overlay.dts
index 524a1c1..a4f6b86 100644 (file)
--- a/arch/arm/boot/dts/overlays/pps-gpio-overlay.dts
+++ b/arch/arm/boot/dts/overlays/pps-gpio-overlay.dts
@@ -34,5 +34,6 @@
                          <&pps_pins>,"reg:0";
                assert_falling_edge = <&pps>,"assert-falling-edge?";
                capture_clear = <&pps>,"capture-clear?";
+               pull = <&pps_pins>,"brcm,pull:0";
        };
 };