[PATCH v3 3/6] dt-bindings: memory: Add Baikal-T1 L2-cache Control Block binding

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

There is a single register provided by the SoC system controller,
which can be used to tune the L2-cache RAM up. It only provides a way
to change the L2-RAM access latencies. So aside from "be,bt1-l2-ctl"
compatible string the device node can be optionally equipped with the
properties of Tag/Data/WS latencies.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Olof Johansson <olof@lixom.net>
Cc: linux-mips@vger.kernel.org
Cc: soc@kernel.org

---

Changelog v2:
- Move driver to the memory subsystem.
- Use dual GPL/BSD license.
- Use single lined copyright header.
- Move "allOf" restrictions to the root level of the properties.
- Discard syscon compatible string and reg property.
- The DT node is supposed to be a child of the Baikal-T1 system controller
  node.

Changelog v3:
- Get the reg property back even though the driver is using the parental
  syscon regmap.
- The DT schema will live separately from the system controller, but the
  corresponding sub-node of the later DT schema will $ref this one.
- Set non-default latencies in the example.
---
 .../memory-controllers/baikal,bt1-l2-ctl.yaml | 63 +++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/memory-controllers/baikal,bt1-l2-ctl.yaml

diff --git a/Documentation/devicetree/bindings/memory-controllers/baikal,bt1-l2-ctl.yaml b/Documentation/devicetree/bindings/memory-controllers/baikal,bt1-l2-ctl.yaml
new file mode 100644
index 000000000000..1fca282f64a2
--- /dev/null
+++ b/Documentation/devicetree/bindings/memory-controllers/baikal,bt1-l2-ctl.yaml
@@ -0,0 +1,63 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/memory-controllers/baikal,bt1-l2-ctl.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Baikal-T1 L2-cache Control Block
+
+maintainers:
+  - Serge Semin <fancer.lancer@gmail.com>
+
+description: |
+  By means of the System Controller Baikal-T1 SoC exposes a few settings to
+  tune the MIPS P5600 CM2 L2 cache performance up. In particular it's possible
+  to change the Tag, Data and Way-select RAM access latencies. Baikal-T1
+  L2-cache controller block is responsible for the tuning. Its DT node is
+  supposed to be a child of the system controller.
+
+properties:
+  compatible:
+    const: baikal,bt1-l2-ctl
+
+  reg:
+    maxItems: 1
+
+  baikal,l2-ws-latency:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: Cycles of latency for Way-select RAM accesses
+    default: 0
+    minimum: 0
+    maximum: 3
+
+  baikal,l2-tag-latency:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: Cycles of latency for Tag RAM accesses
+    default: 0
+    minimum: 0
+    maximum: 3
+
+  baikal,l2-data-latency:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: Cycles of latency for Data RAM accesses
+    default: 1
+    minimum: 0
+    maximum: 3
+
+additionalProperties: false
+
+required:
+  - compatible
+
+examples:
+  - |
+    l2@1f04d028 {
+      compatible = "baikal,bt1-l2-ctl";
+      reg = <0x1f04d028 0x004>;
+
+      baikal,l2-ws-latency = <1>;
+      baikal,l2-tag-latency = <1>;
+      baikal,l2-data-latency = <2>;
+    };
+...
-- 
2.26.2