[PATCH v3 1/3] dt-bindings: nvmem: layouts: Add PSCRR NVMEM layout

[Faruque Ansari <faruque.ansari@oss.qualcomm.com>]

Add a schema for the PSCRR NVMEM layout, which persists the power
state change reason in a single NVMEM cell so it survives a power
cycle and can be read back on the next boot.

Signed-off-by: Faruque Ansari <faruque.ansari@oss.qualcomm.com>
---
 .../bindings/nvmem/layouts/nvmem-layout.yaml       |  1 +
 .../bindings/nvmem/layouts/pscrr-nvmem.yaml        | 87 ++++++++++++++++++++++
 MAINTAINERS                                        |  1 +
 3 files changed, 89 insertions(+)

diff --git a/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml b/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml
index 382507060651..24545db61416 100644
--- a/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml
+++ b/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml
@@ -21,6 +21,7 @@ oneOf:
   - $ref: fixed-layout.yaml
   - $ref: kontron,sl28-vpd.yaml
   - $ref: onie,tlv-layout.yaml
+  - $ref: pscrr-nvmem.yaml
   - $ref: u-boot,env.yaml
 
 properties:
diff --git a/Documentation/devicetree/bindings/nvmem/layouts/pscrr-nvmem.yaml b/Documentation/devicetree/bindings/nvmem/layouts/pscrr-nvmem.yaml
new file mode 100644
index 000000000000..118669d33f5c
--- /dev/null
+++ b/Documentation/devicetree/bindings/nvmem/layouts/pscrr-nvmem.yaml
@@ -0,0 +1,87 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/nvmem/layouts/pscrr-nvmem.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NVMEM layout for the Power State Change Reason recorder (PSCRR)
+
+maintainers:
+  - Faruque Ansari <faruque.ansari@oss.qualcomm.com>
+  - Oleksij Rempel <o.rempel@pengutronix.de>
+
+description:
+  An NVMEM layout for a Power State Change Reason (PSCRR) recorder. The
+  reboot or shutdown cause is persisted into a single small NVMEM cell,
+  such as an RTC scratch register, a PMIC SDAM (Scratch Data Access Memory)
+  byte, or an EEPROM byte, so the reason survives a power cycle and can be
+  read back on the next boot.
+
+select: false
+
+properties:
+  compatible:
+    const: pscrr-nvmem
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 1
+
+patternProperties:
+  "^.*@[0-9a-f]+$":
+    type: object
+    description:
+      The single NVMEM cell used to persist the power state change reason.
+
+    properties:
+      reg:
+        items:
+          - items:
+              - description: Offset, in bytes, of the cell within the
+                  parent NVMEM device.
+              - const: 1
+        description:
+          Offset and size, in bytes, of the cell within the parent NVMEM
+          device. The reason value occupies a single byte, so the size
+          must be 1.
+
+      bits:
+        $ref: /schemas/types.yaml#/definitions/uint32-array
+        items:
+          - minimum: 0
+            maximum: 7
+            description:
+              Bit offset within the byte addressed by reg.
+          - minimum: 1
+            maximum: 8
+            description:
+              Number of bits used to store the reason. Must be wide enough
+              to hold every value of enum psc_reason (currently 4 bits or
+              more).
+        description:
+          Optional. When absent, the whole byte addressed by reg is used.
+
+    required:
+      - reg
+
+    additionalProperties: false
+
+required:
+  - compatible
+
+additionalProperties: false
+
+examples:
+  - |
+    nvmem-layout {
+        compatible = "pscrr-nvmem";
+        #address-cells = <1>;
+        #size-cells = <1>;
+
+        reboot-reason-persist@49 {
+            reg = <0x49 0x1>;
+            bits = <0 4>;
+        };
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index 19b9f6605d98..51f31e95f4ea 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -21693,6 +21693,7 @@ R:	Pengutronix Kernel Team <kernel@pengutronix.de>
 L:	linux-pm@vger.kernel.org
 S:	Maintained
 F:	Documentation/ABI/testing/sysfs-kernel-pscrr
+F:	Documentation/devicetree/bindings/nvmem/layouts/pscrr-nvmem.yaml
 F:	drivers/power/reset/pscrr/
 F:	include/linux/pscrr.h
 F:	tools/testing/selftests/pscrr/

-- 
2.34.1