[PATCH v7 1/2] dt-bindings: cpufreq: Document support for Airoha EN7581 CPUFreq

[Christian Marangi <ansuelsmth@gmail.com>]

On newer Airoha SoC, CPU Frequency is scaled indirectly with SMC commands
to ATF.

A virtual clock is exposed. This virtual clock is a get-only clock and
is used to expose the current global CPU clock. The frequency info comes
by the output of the SMC command that reports the clock in MHz.

The SMC sets the CPU clock by providing an index, this is modelled as
performance states in a power domain.

CPUs can't be individually scaled as the CPU frequency is shared across
all CPUs and is global.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
---
Changes v7:
- Add more info to the description for usage of clock and
  performance-domain
- Drop redundant nodes from example
Changes v6:
- No changes
Changes v5:
- Add Reviewed-by tag
- Fix OPP node name error
- Rename cpufreq node name to power-domain
- Rename CPU node power domain name to perf
- Add model and compatible to example
Changes v4:
- Add this patch

 .../cpufreq/airoha,en7581-cpufreq.yaml        | 55 +++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/cpufreq/airoha,en7581-cpufreq.yaml

diff --git a/Documentation/devicetree/bindings/cpufreq/airoha,en7581-cpufreq.yaml b/Documentation/devicetree/bindings/cpufreq/airoha,en7581-cpufreq.yaml
new file mode 100644
index 000000000000..7d4510b3219c
--- /dev/null
+++ b/Documentation/devicetree/bindings/cpufreq/airoha,en7581-cpufreq.yaml
@@ -0,0 +1,55 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/cpufreq/airoha,en7581-cpufreq.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Airoha EN7581 CPUFreq
+
+maintainers:
+  - Christian Marangi <ansuelsmth@gmail.com>
+
+description: |
+  On newer Airoha SoC, CPU Frequency is scaled indirectly with SMC commands
+  to ATF.
+
+  A virtual clock is exposed. This virtual clock is a get-only clock and
+  is used to expose the current global CPU clock. The frequency info comes
+  by the output of the SMC command that reports the clock in MHz.
+
+  The SMC sets the CPU clock by providing an index, this is modelled as
+  performance states in a power domain.
+
+  CPUs can't be individually scaled as the CPU frequency is shared across
+  all CPUs and is global.
+
+properties:
+  compatible:
+    const: airoha,en7581-cpufreq
+
+  '#clock-cells':
+    const: 0
+
+  '#power-domain-cells':
+    const: 0
+
+  operating-points-v2: true
+
+required:
+  - compatible
+  - '#clock-cells'
+  - '#power-domain-cells'
+  - operating-points-v2
+
+additionalProperties: false
+
+examples:
+  - |
+    performance-domain {
+        compatible = "airoha,en7581-cpufreq";
+
+        operating-points-v2 = <&cpu_smcc_opp_table>;
+
+        #power-domain-cells = <0>;
+        #clock-cells = <0>;
+    };
-- 
2.45.2