[PATCH RFC v2 06/11] dt-bindings: remoteproc: add remoteproc-virtio

[Francesco Valla <francesco@valla.it>]

Add a new binding to describe remoteproc-provided virtio devices; while
these are discovered through a resource table parsed by the remoteproc
infrastructure at runtime, their description can be needed to probe
non-discoverable buses (such as I2C) or to link consumers and suppliers.

Each vdev is described by a dedicated "group" node, which then includes
a virtio-device node. Each vdev shall be statically linked to a "group"
node using its index inside the resource table as the reg property of
the node; this permits to have multiple instances of the same type of
device.

The binding is intended to be generic and adopted by any remoteproc
provider.

Signed-off-by: Francesco Valla <francesco@valla.it>
---
 .../bindings/remoteproc/remoteproc-virtio.yaml     | 106 +++++++++++++++++++++
 1 file changed, 106 insertions(+)

diff --git a/Documentation/devicetree/bindings/remoteproc/remoteproc-virtio.yaml b/Documentation/devicetree/bindings/remoteproc/remoteproc-virtio.yaml
new file mode 100644
index 000000000000..8cdfa8d0f936
--- /dev/null
+++ b/Documentation/devicetree/bindings/remoteproc/remoteproc-virtio.yaml
@@ -0,0 +1,106 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/remoteproc/remoteproc-virtio.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Virtio devices over remoteproc
+
+description: |
+  Virtio devices ("vdevs") can be exposed using the remoteproc infrastructure
+  and its resource table. For some of them, a device tree node might be needed
+  to describe remote undiscoverable hardware and/or connect consumers and
+  providers.
+
+maintainers:
+  - Francesco Valla <francesco@valla.it>
+
+properties:
+  virtio:
+    type: object
+    description: |
+      Contains a group of virtio devices exposed by the firmware running on
+      the remote processor through its resource table.
+
+    additionalProperties: false
+
+    properties:
+      '#address-cells':
+        const: 1
+
+      '#size-cells':
+        const: 0
+
+    patternProperties:
+      "@[0-9a-f]+$":
+        type: object
+        description: |
+          A single virtio device exposed by the remote processor. It can
+          contain at most one child node, describing the virtio device itself
+          (e.g., to declare devices on a non-discoverable bus or to act as a
+          provider for other nodes).
+
+        properties:
+          reg:
+            description: |
+              Position of the virtio device among the VDEV resources contained
+              inside the resource table.
+            maxItems: 1
+
+          memory-region:
+            description: |
+              Memory region used for the buffers exchanged with the remote
+              processor. A restricted-dma-pool region forces all buffers to
+              be bounced through it.
+            maxItems: 1
+
+        additionalProperties:
+          type: object
+          $ref: /schemas/virtio/virtio-device.yaml#
+
+        required:
+          - reg
+
+    required:
+      - '#address-cells'
+      - '#size-cells'
+
+additionalProperties: true
+
+examples:
+  - |
+    remoteproc-cm33 {
+        virtio {
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            vdev@0 {
+                reg = <0>;
+
+                gpio {
+                    compatible = "virtio,device29";
+
+                    gpio-controller;
+                    #gpio-cells = <2>;
+                };
+            };
+
+            vdev@1 {
+                reg = <1>;
+                memory-region = <&vdev1_buffer>;
+
+                i2c {
+                    compatible = "virtio,device22";
+
+                    #address-cells = <1>;
+                    #size-cells = <0>;
+
+                    eeprom@50 {
+                        compatible = "atmel,24c1025";
+                        reg = <0x50>;
+                    };
+                };
+            };
+        };
+    };
+...

-- 
2.56.0