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Message-Id: <20250923113441.555284-1-lakshay.piplani@nxp.com>
Date: Tue, 23 Sep 2025 17:04:40 +0530
From: Lakshay Piplani <lakshay.piplani@....com>
To: alexandre.belloni@...tlin.com,
linux-rtc@...r.kernel.org,
linux-kernel@...r.kernel.org,
robh@...nel.org,
krzk+dt@...nel.org,
conor+dt@...nel.org,
devicetree@...r.kernel.org
Cc: pankit.garg@....com,
vikash.bansal@....com,
priyanka.jain@....com,
shashank.rebbapragada@....com,
Lakshay Piplani <lakshay.piplani@....com>
Subject: [PATCH v4 1/2] dt-bindings: rtc: Add pcf85053 support
Add device tree bindings for NXP PCF85053 RTC chip.
Signed-off-by: Pankit Garg <pankit.garg@....com>
Signed-off-by: Lakshay Piplani <lakshay.piplani@....com>
---
V3 -> V4: Add dedicated nxp,pcf85053.yaml.
Remove entry from trivial-rtc.yaml.
V2 -> V3: Moved MAINTAINERS file changes to the driver patch
V1 -> V2: Handled dt-bindings by trivial-rtc.yaml
.../devicetree/bindings/rtc/nxp,pcf85053.yaml | 128 ++++++++++++++++++
1 file changed, 128 insertions(+)
create mode 100644 Documentation/devicetree/bindings/rtc/nxp,pcf85053.yaml
diff --git a/Documentation/devicetree/bindings/rtc/nxp,pcf85053.yaml b/Documentation/devicetree/bindings/rtc/nxp,pcf85053.yaml
new file mode 100644
index 000000000000..6b1c97358486
--- /dev/null
+++ b/Documentation/devicetree/bindings/rtc/nxp,pcf85053.yaml
@@ -0,0 +1,128 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright 2025 NXP
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/nxp,pcf85053.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NXP PCF85053 Real Time Clock
+
+maintainers:
+ - Pankit Garg <pankit.garg@....com>
+ - Lakshay Piplani <lakshay.piplani@....com>
+
+properties:
+ compatible:
+ enum:
+ - nxp,pcf85053
+
+ reg:
+ maxItems: 1
+
+ interrupts:
+ maxItems: 1
+
+ nxp,interface:
+ $ref: /schemas/types.yaml#/definitions/string
+ enum: [ primary, secondary ]
+ description: |
+ Identifies this host's logical role in a multi-host topology for the
+ PCF85053 RTC. The device exposes a "TWO" ownership bit in the CTRL
+ register that gates which host may write time/alarm registers.
+ - "primary": Designated host that *may* claim write ownership (set
+ CTRL.TWO=1) **if** write-access is explicitly requested.
+ - "secondary": Peer host that writes only when CTRL.TWO=0 (default).
+
+ nxp,write-access:
+ type: boolean
+ description: |
+ Request the driver to claim write ownership at probe time by setting
+ CTRL.TWO=1. This property is only valid when nxp,interface="primary".
+ The driver will not modify any other CTRL bits (HF/DM/etc.) and will not
+ clear any status/interrupt flags at probe.
+
+required:
+ - compatible
+ - reg
+ - nxp,interface
+
+additionalProperties: false
+
+# Schema constraints matching driver:
+# 1) If nxp,write-access is present, nxp,interface must be "primary".
+# Rationale: only the primary may claim ownership; driver will set TWO=1.
+# 2) If nxp,interface is "secondary", nxp,write-access must not be present.
+# Rationale: secondary never claims ownership and cannot write CTRL/ST/alarm.
+#
+# Practical effect:
+# - Primary without 'nxp,write-access'; primary is read only; secondary may
+# write time registers.
+# - Primary with 'nxp,write-access'; primary owns writes, secondary is read only.
+allOf:
+ - $ref: rtc.yaml#
+ - oneOf:
+ # Case 1: primary with write-access
+ - required: [ "nxp,write-access" ]
+ properties:
+ nxp,interface:
+ const: primary
+
+ # Case 2: primary without write-access
+ - properties:
+ nxp,interface:
+ const: primary
+ not:
+ required: [ "nxp,write-access" ]
+
+ # Case 3: secondary (must not have write-access)
+ - properties:
+ nxp,interface:
+ const: secondary
+ not:
+ required: [ "nxp,write-access" ]
+
+examples:
+ # Single host example.
+ - |
+ #include <dt-bindings/interrupt-controller/irq.h>
+ i2c {
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ rtc@6f {
+ compatible = "nxp,pcf85053";
+ reg = <0x6f>;
+ nxp,interface = "primary";
+ nxp,write-access;
+ interrupt-parent = <&gpio2>;
+ interrupts = <3 IRQ_TYPE_EDGE_FALLING>;
+ };
+ };
+
+ # Dual-host example: one primary that claims writes; one secondary that never claims writes.
+ - |
+ #include <dt-bindings/interrupt-controller/irq.h>
+ i2c0 {
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ rtc@6f {
+ compatible = "nxp,pcf85053";
+ reg = <0x6f>;
+ nxp,interface = "primary";
+ nxp,write-access;
+ interrupt-parent = <&gpio2>;
+ interrupts = <3 IRQ_TYPE_EDGE_FALLING>;
+ };
+ };
+
+ i2c1 {
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ rtc@6f {
+ compatible = "nxp,pcf85053";
+ reg = <0x6f>;
+ nxp,interface = "secondary";
+ };
+ };
--
2.25.1
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