[PATCH v2 1/3] dt-bindings: rtc: pcf8523: add DSM pm option for battery switch-over

[miguelborgesdefreitas@gmail.com]

From: Miguel Borges de Freitas <miguelborgesdefreitas@gmail.com>

This adds direct-switching mode as a configurable DT flag for
RTC modules supporting it (e.g. nxp pcf8523).
DSM switches the power source to the battery supply whenever the
VDD drops below VBAT. The option is recommended for hw designs
where VDD is always expected to be higher than VBAT.

Signed-off-by: Miguel Borges de Freitas <miguelborgesdefreitas@gmail.com>
---
Changes in v2:
- Added extended commit message for git history
- Separate dt bindings documentation into a single patch

 Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt | 7 ++++++-
 Documentation/devicetree/bindings/rtc/rtc.yaml        | 7 +++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt b/Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt
index 0b1080c..f715a8f 100644
--- a/Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt
+++ b/Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt
@@ -4,10 +4,14 @@ Required properties:
 - compatible: Should contain "nxp,pcf8523".
 - reg: I2C address for chip.
 
-Optional property:
+Optional properties:
 - quartz-load-femtofarads: The capacitive load of the quartz(x-tal),
   expressed in femto Farad (fF). Valid values are 7000 and 12500.
   Default value (if no value is specified) is 12500fF.
+- pm-enable-dsm: battery switch-over function is enabled in direct
+  switching mode. The power failure condition happens when VDD < VBAT,
+  without requiring VDD to drop below Vth(sw)bat.
+  Default value (if not provided) is the standard mode.
 
 Example:
 
@@ -15,4 +19,5 @@ pcf8523: rtc@68 {
 	compatible = "nxp,pcf8523";
 	reg = <0x68>;
 	quartz-load-femtofarads = <7000>;
+	pm-enable-dsm;
 };
diff --git a/Documentation/devicetree/bindings/rtc/rtc.yaml b/Documentation/devicetree/bindings/rtc/rtc.yaml
index ee237b2..a0048f4 100644
--- a/Documentation/devicetree/bindings/rtc/rtc.yaml
+++ b/Documentation/devicetree/bindings/rtc/rtc.yaml
@@ -47,4 +47,11 @@ properties:
     description:
       Enables wake up of host system on alarm.
 
+  pm-enable-dsm:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description:
+      Enables the battery switch-over function in direct switching
+      mode. Should be set in systems where VDD is higher than VBAT
+      at all times.
+
 ...
-- 
1.8.3.1