[PATCH v3 1/3] dt-bindings: hwmon: Add Baikal-T1 PVT sensor binding

[Serge Semin <Sergey.Semin@baikalelectronics.ru>]

Baikal-T1 SoC is equipped with an embedded process, voltage and
temperature sensor to monitor the chip internal environment like
temperature, supply voltage and transistors performance.

This bindings describes the external Baikal-T1 PVT control interfaces
like MMIO registers space, interrupt request number and clocks source.
These are then used by the corresponding hwmon device driver to
implement the sysfs files-based access to the sensors functionality.

Co-developed-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
Signed-off-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-mips@vger.kernel.org

---

Changelog v2:
- Lowercase the node-name in the example.
- Add dual-license header.
- Don't use a multi-arg clock phandle reference in the examples dt-binding
  property. Thus reundant include pre-processor statement can be removed.
- Replace "additionalProperties: false" property with
  "unevaluatedProperties: false".
- Discard label definition from the example.
- Align settings of the "#thermal-sensor-cells" property with two spaces
  ahead of the property line start.

Changelog v3:
- Add "baikal,pvt-temp-trim-millicelsius" property support.
---
 .../bindings/hwmon/baikal,bt1-pvt.yaml        | 107 ++++++++++++++++++
 1 file changed, 107 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/baikal,bt1-pvt.yaml

diff --git a/Documentation/devicetree/bindings/hwmon/baikal,bt1-pvt.yaml b/Documentation/devicetree/bindings/hwmon/baikal,bt1-pvt.yaml
new file mode 100644
index 000000000000..6c3a44ec3684
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/baikal,bt1-pvt.yaml
@@ -0,0 +1,107 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/hwmon/baikal,bt1-pvt.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Baikal-T1 PVT Sensor
+
+maintainers:
+  - Serge Semin <fancer.lancer@gmail.com>
+
+description: |
+  Baikal-T1 SoC provides an embedded process, voltage and temperature
+  sensor to monitor an internal SoC environment (chip temperature, supply
+  voltage and process monitor) and on time detect critical situations,
+  which may cause the system instability and even damages. The IP-block
+  is based on the Analog Bits PVT sensor, but is equipped with a dedicated
+  control wrapper, which provides a MMIO registers-based access to the
+  sensor core functionality (APB3-bus based) and exposes an additional
+  functions like thresholds/data ready interrupts, its status and masks,
+  measurements timeout. Its internal structure is depicted on the next
+  diagram:
+
+     Analog Bits core                     Bakal-T1 PVT control block
+  +--------------------+                  +------------------------+
+  | Temperature sensor |-+         +------| Sensors control        |
+  |--------------------| |<---En---|      |------------------------|
+  | Voltage sensor     |-|<--Mode--| +--->| Sampled data           |
+  |--------------------| |<--Trim--+ |    |------------------------|
+  | Low-Vt sensor      |-|           | +--| Thresholds comparator  |
+  |--------------------| |---Data----| |  |------------------------|
+  | High-Vt sensor     |-|           | +->| Interrupts status      |
+  |--------------------| |--Valid--+-+ |  |------------------------|
+  | Standard-Vt sensor |-+         +---+--| Interrupts mask        |
+  +--------------------+                  |------------------------|
+           ^                              | Interrupts timeout     |
+           |                              +------------------------+
+           |                                        ^  ^
+  Rclk-----+----------------------------------------+  |
+  APB3-------------------------------------------------+
+
+  This bindings describes the external Baikal-T1 PVT control interfaces
+  like MMIO registers space, interrupt request number and clocks source.
+  These are then used by the corresponding hwmon device driver to
+  implement the sysfs files-based access to the sensors functionality.
+
+properties:
+  compatible:
+    const: baikal,bt1-pvt
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    items:
+      - description: PVT reference clock
+      - description: APB3 interface clock
+
+  clock-names:
+    items:
+      - const: ref
+      - const: pclk
+
+  "#thermal-sensor-cells":
+    description: Baikal-T1 can be referenced as the CPU thermal-sensor
+    const: 0
+
+  baikal,pvt-temp-trim-millicelsius:
+    description: |
+      Temperature sensor trimming factor. It can be used to manually adjust the
+      temperature measurements within 7.130 degrees Celsius.
+    maxItems: 1
+    items:
+      default: 0
+      minimum: 0
+      maximum: 7130
+
+unevaluatedProperties: false
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+  - clock-names
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/mips-gic.h>
+
+    pvt@1f200000 {
+      compatible = "baikal,bt1-pvt";
+      reg = <0x1f200000 0x1000>;
+      #thermal-sensor-cells = <0>;
+
+      interrupts = <GIC_SHARED 31 IRQ_TYPE_LEVEL_HIGH>;
+
+      baikal,pvt-temp-trim-millicelsius = <1000>;
+
+      clocks = <&ccu_sys>, <&ccu_sys>;
+      clock-names = "ref", "pclk";
+    };
+...
-- 
2.26.2