[PATCH v3 1/3] dt-bindings: nvmem: layouts: Add PSCRR NVMEM layout
From: Faruque Ansari <hidden>
Date: 2026-09-14 04:39:20
Also in:
linux-arm-msm, linux-pm, linux-watchdog, lkml
Subsystem:
nvmem framework, open firmware and flattened device tree bindings, the rest · Maintainers:
Srinivas Kandagatla, Rob Herring, Krzysztof Kozlowski, Conor Dooley, Linus Torvalds
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 <redacted> --- .../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/
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2.34.1