[PATCH 1/1] dt-bindings: T-HEAD CLINT

[Heinrich Schuchardt <heinrich.schuchardt@canonical.com>]

The CLINT in the T-HEAD 9xx CPUs is similar to the SiFive CLINT but does
not support 64bit mmio access to the MTIMER device.

OpenSBI currently uses a property 'clint,has-no-64bit-mmio' to indicate the
restriction and the "sifive,cling0" compatible string. An OpenSBI
patch suggested to use "reg-io-width = <4>;" as the reg-io-width property
is generally used in the devicetree schema for such a condition.

As the design is not SiFive based it is preferable to apply a compatible
string identifying T-HEAD instead.

Add a new yaml file describing the T-HEAD CLINT.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
---
@Palmer, @Anup
I copied you as maintainers from sifive,clint.yaml. Please, indicate if
this should be changed.

For the prior discussion see:
https://lore.kernel.org/all/20211015100941.17621-1-heinrich.schuchardt@canonical.com/
https://lore.kernel.org/all/20211015120735.27972-1-heinrich.schuchardt@canonical.com/

A release candidate of the ACLINT specification is available at
https://github.com/riscv/riscv-aclint/releases
---
 .../bindings/timer/thead,clint.yaml           | 62 +++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/timer/thead,clint.yaml

diff --git a/Documentation/devicetree/bindings/timer/thead,clint.yaml b/Documentation/devicetree/bindings/timer/thead,clint.yaml
new file mode 100644
index 000000000000..02463fb2043a
--- /dev/null
+++ b/Documentation/devicetree/bindings/timer/thead,clint.yaml
@@ -0,0 +1,62 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/timer/thead,clint.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: SiFive Core Local Interruptor
+
+maintainers:
+  - Palmer Dabbelt <palmer@dabbelt.com>
+  - Anup Patel <anup.patel@wdc.com>
+
+description:
+  T-HEAD (and other RISC-V) SOCs include an implementation of the T-HEAD
+  Core Local Interruptor (CLINT) for M-mode timer and M-mode inter-processor
+  interrupts. It directly connects to the timer and inter-processor interrupt
+  lines of various HARTs (or CPUs) so RISC-V per-HART (or per-CPU) local
+  interrupt controller is the parent interrupt controller for CLINT device.
+  The clock frequency of the CLINT is specified via "timebase-frequency" DT
+  property of "/cpus" DT node. The "timebase-frequency" DT property is
+  described in Documentation/devicetree/bindings/riscv/cpus.yaml
+
+properties:
+  compatible:
+    items:
+      - const:
+          - allwinner,sun20i-d1-clint
+      - const:
+          - thead,clint0
+
+    description:
+      Should be "<vendor>,<chip>-clint" and "thead,clint<version>" for
+      the T-HEAD derived CLINTs.
+      Supported compatible strings are -
+      "allwinner,sun20i-d1-clint" for the CLINT in the Allwinner D1 SoC
+      and "thead,clint0" for the T-HEAD IP block with no chip
+      integration tweaks.
+
+  reg:
+    maxItems: 1
+
+  interrupts-extended:
+    minItems: 1
+
+additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - interrupts-extended
+
+examples:
+  - |
+    timer@2000000 {
+      compatible = "allwinner,sun20i-d1-clint", "thead,clint0";
+      interrupts-extended = <&cpu1intc 3 &cpu1intc 7
+                             &cpu2intc 3 &cpu2intc 7
+                             &cpu3intc 3 &cpu3intc 7
+                             &cpu4intc 3 &cpu4intc 7>;
+       reg = <0x2000000 0x10000>;
+    };
+...
-- 
2.32.0