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[v3,2/3] dt-bindings: m41t80: add xtal load capacitance

Message ID 20230119213903.899756-3-dennis@sparkcharge.io
State New
Headers show
Series rtc: Set M41T82 & M41T83 xtal load capacitance from DT | expand

Commit Message

Dennis Lambe Jan. 19, 2023, 9:39 p.m. UTC 
The ST m41t82 and m41t83 support programmable load capacitance from 3.5
pF to 17.4 pF. The hardware defaults to 12.5 pF.

The accuracy of the xtal can be calibrated precisely by adjusting the
load capacitance.

Add default, minimum, and maximum for the standard rtc property
quartz-load-femtofarads on compatible devices.

Signed-off-by: Dennis Lambe Jr <dennis@sparkcharge.io>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
---

Notes:
    v2 -> v3:
    	added "Reviewed-by: Krzysztof Kozlowski" to changelog
    
    v1 -> v2:
    	remove accidental wakeup-sources line
    		suggested by Krzysztof Kozlowski
    	spelling fix in changelog

 .../devicetree/bindings/rtc/st,m41t80.yaml       | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
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Patch

diff --git a/Documentation/devicetree/bindings/rtc/st,m41t80.yaml b/Documentation/devicetree/bindings/rtc/st,m41t80.yaml
index fc9c6da6483f..6673adf6e99b 100644
--- a/Documentation/devicetree/bindings/rtc/st,m41t80.yaml
+++ b/Documentation/devicetree/bindings/rtc/st,m41t80.yaml
@@ -33,6 +33,11 @@  properties:
   "#clock-cells":
     const: 1
 
+  quartz-load-femtofarads:
+    default: 12500
+    minimum: 3500
+    maximum: 17375
+
   clock-output-names:
     maxItems: 1
     description: From common clock binding to override the default output clock name.
@@ -46,6 +51,17 @@  properties:
 
 allOf:
   - $ref: rtc.yaml
+  - if:
+      not:
+        properties:
+          compatible:
+            contains:
+              enum:
+                - st,m41t82
+                - st,m41t83
+    then:
+      properties:
+        quartz-load-femtofarads: false
 
 unevaluatedProperties: false