linux-kernel - [PATCH 2/3] dt-bindings: m41t80: add xtal load capacitance

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Message-Id: <20221219190915.3912384-3-dennis@sparkcharge.io>
Date:   Mon, 19 Dec 2022 19:09:14 +0000
From:   Dennis Lambe Jr <dennis@...rkcharge.io>
To:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rtc@...r.kernel.org, Alexander Bigga <ab@...able.de>,
        Dennis Lambe Jr <dennis@...rkcharge.io>
Subject: [PATCH 2/3] dt-bindings: m41t80: add xtal load capacitance

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 capacicance.

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

Signed-off-by: Dennis Lambe Jr <dennis@...rkcharge.io>
---
 .../devicetree/bindings/rtc/st,m41t80.yaml     | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/Documentation/devicetree/bindings/rtc/st,m41t80.yaml b/Documentation/devicetree/bindings/rtc/st,m41t80.yaml
index fc9c6da6483f..6b72580dc031 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.
@@ -44,8 +49,21 @@ properties:
       clock-frequency:
         const: 32768
 
+  wakeup-source: true
+
 allOf:
   - $ref: rtc.yaml
+  - if:
+      not:
+        properties:
+          compatible:
+            contains:
+              enum:
+                - st,m41t82
+                - st,m41t83
+    then:
+      properties:
+        quartz-load-femtofarads: false
 
 unevaluatedProperties: false
 
-- 
2.25.1