linux-kernel - [PATCH v3 2/3] dt-bindings: m41t80: add xtal load capacitance

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Message-Id: <20230119213903.899756-3-dennis@sparkcharge.io>
Date:   Thu, 19 Jan 2023 21:39:02 +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>,
        Atsushi Nemoto <atsushi.nemoto@...d.co.jp>
Cc:     Mylène Josserand 
        <mylene.josserand@...e-electrons.com>,
        Gary Bisson <gary.bisson@...ndarydevices.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Troy Kisky <troy.kisky@...ndarydevices.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rtc@...r.kernel.org, Dennis Lambe Jr <dennis@...rkcharge.io>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: [PATCH v3 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 capacitance.

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>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.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(+)

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
 
-- 
2.25.1