[PATCH v11 01/14] dt-bindings: Add PECI subsystem document

[Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>]

This commit adds PECI subsystem document.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Jeffery <andrew@aj.id.au>
Cc: Joel Stanley <joel@jms.id.au>
Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
---
Changes since v10:
- Changed documents format to DT schema format so I dropped all review tags.
  Please review it again.

 .../devicetree/bindings/peci/peci-bus.yaml    | 129 ++++++++++++++++++
 .../devicetree/bindings/peci/peci-client.yaml |  54 ++++++++
 2 files changed, 183 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/peci/peci-bus.yaml
 create mode 100644 Documentation/devicetree/bindings/peci/peci-client.yaml

diff --git a/Documentation/devicetree/bindings/peci/peci-bus.yaml b/Documentation/devicetree/bindings/peci/peci-bus.yaml
new file mode 100644
index 000000000000..b085e67089cf
--- /dev/null
+++ b/Documentation/devicetree/bindings/peci/peci-bus.yaml
@@ -0,0 +1,129 @@
+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/peci/peci-bus.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Generic Device Tree Bindings for PECI bus
+
+maintainers:
+  - Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
+
+description: |
+  PECI (Platform Environment Control Interface) is a one-wire bus interface that
+  provides a communication channel from Intel processors and chipset components
+  to external monitoring or control devices. PECI is designed to support the
+  following sideband functions:
+
+  * Processor and DRAM thermal management
+    - Processor fan speed control is managed by comparing Digital Thermal
+      Sensor (DTS) thermal readings acquired via PECI against the
+      processor-specific fan speed control reference point, or TCONTROL. Both
+      TCONTROL and DTS thermal readings are accessible via the processor PECI
+      client. These variables are referenced to a common temperature, the TCC
+      activation point, and are both defined as negative offsets from that
+      reference.
+    - PECI based access to the processor package configuration space provides
+      a means for Baseboard Management Controllers (BMC) or other platform
+      management devices to actively manage the processor and memory power
+      and thermal features.
+
+  * Platform Manageability
+    - Platform manageability functions including thermal, power, and error
+      monitoring. Note that platform 'power' management includes monitoring
+      and control for both the processor and DRAM subsystem to assist with
+      data center power limiting.
+    - PECI allows read access to certain error registers in the processor MSR
+      space and status monitoring registers in the PCI configuration space
+      within the processor and downstream devices.
+    - PECI permits writes to certain registers in the processor PCI
+      configuration space.
+
+  * Processor Interface Tuning and Diagnostics
+    - Processor interface tuning and diagnostics capabilities
+      (Intel Interconnect BIST). The processors Intel Interconnect Built In
+      Self Test (Intel IBIST) allows for infield diagnostic capabilities in
+      the Intel UPI and memory controller interfaces. PECI provides a port to
+      execute these diagnostics via its PCI Configuration read and write
+      capabilities.
+
+  * Failure Analysis
+    - Output the state of the processor after a failure for analysis via
+      Crashdump.
+
+  PECI uses a single wire for self-clocking and data transfer. The bus
+  requires no additional control lines. The physical layer is a self-clocked
+  one-wire bus that begins each bit with a driven, rising edge from an idle
+  level near zero volts. The duration of the signal driven high depends on
+  whether the bit value is a logic '0' or logic '1'. PECI also includes
+  variable data transfer rate established with every message. In this way, it
+  is highly flexible even though underlying logic is simple.
+
+  The interface design was optimized for interfacing between an Intel
+  processor and chipset components in both single processor and multiple
+  processor environments. The single wire interface provides low board
+  routing overhead for the multiple load connections in the congested routing
+  area near the processor and chipset components. Bus speed, error checking,
+  and low protocol overhead provides adequate link bandwidth and reliability
+  to transfer critical device operating conditions and configuration
+  information.
+
+  PECI subsystem provides single or multiple bus nodes support so each bus can
+  have one adapter node and multiple device specific client nodes that can be
+  attached to the PECI bus so each processor client's features can be supported
+  by the client node through an adapter connection in the bus.
+
+properties:
+  compatible:
+    const: simple-bus
+
+  "#address-cells":
+    # Required to define bus device control resource address.
+    const: 1
+
+  "#size-cells":
+    # Required to define bus device control resource address.
+    const: 1
+
+  ranges: true
+
+required:
+  - compatible
+  - "#address-cells"
+  - "#size-cells"
+  - ranges
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/clock/ast2600-clock.h>
+    peci: bus@1e78b000 {
+        compatible = "simple-bus";
+        #address-cells = <1>;
+        #size-cells = <1>;
+        ranges = <0x0 0x1e78b000 0x200>;
+
+        peci0: peci-bus@0 {
+            compatible = "aspeed,ast2600-peci";
+            reg = <0x0 0x100>;
+            #address-cells = <1>;
+            #size-cells = <0>;
+            interrupts = <GIC_SPI 38 IRQ_TYPE_LEVEL_HIGH>;
+            clocks = <&syscon ASPEED_CLK_GATE_REF0CLK>;
+            resets = <&syscon ASPEED_RESET_PECI>;
+            clock-frequency = <24000000>;
+        };
+
+        // Just an example. ast2600 doesn't have a second PECI module actually.
+        peci1: peci-bus@100 {
+            compatible = "aspeed,ast2600-peci";
+            reg = <0x100 0x100>;
+            #address-cells = <1>;
+            #size-cells = <0>;
+            interrupts = <GIC_SPI 39 IRQ_TYPE_LEVEL_HIGH>;
+            clocks = <&syscon ASPEED_CLK_GATE_REF0CLK>;
+            resets = <&syscon ASPEED_RESET_PECI>;
+            clock-frequency = <24000000>;
+        };
+    };
+...
diff --git a/Documentation/devicetree/bindings/peci/peci-client.yaml b/Documentation/devicetree/bindings/peci/peci-client.yaml
new file mode 100644
index 000000000000..fc7c4110e929
--- /dev/null
+++ b/Documentation/devicetree/bindings/peci/peci-client.yaml
@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/peci/peci-client.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Generic Device Tree Bindings for PECI clients
+
+maintainers:
+  - Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
+
+properties:
+  compatible:
+    enum:
+      - intel,peci-client
+
+  reg:
+    description: |
+      Address of a client CPU. According to the PECI specification, client
+      addresses start from 0x30.
+    maxItems: 1
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/clock/ast2600-clock.h>
+    peci: bus@1e78b000 {
+        compatible = "simple-bus";
+        #address-cells = <1>;
+        #size-cells = <1>;
+        ranges = <0x0 0x1e78b000 0x60>;
+
+        peci0: peci-bus@0 {
+            compatible = "aspeed,ast2600-peci";
+            reg = <0x0 0x100>;
+            #address-cells = <1>;
+            #size-cells = <0>;
+            interrupts = <GIC_SPI 38 IRQ_TYPE_LEVEL_HIGH>;
+            clocks = <&syscon ASPEED_CLK_GATE_REF0CLK>;
+            resets = <&syscon ASPEED_RESET_PECI>;
+            clock-frequency = <24000000>;
+
+            peci-client@30 {
+                compatible = "intel,peci-client";
+                reg = <0x30>;
+            };
+
+            peci-client@31 {
+                compatible = "intel,peci-client";
+                reg = <0x31>;
+            };
+        };
+    };
+...
-- 
2.17.1