Re: [PATCH 06/13] dt-bindings: rng: add bindings for microchip mpfs rng

On Wed, Nov 10, 2021 at 09:46:23AM +0000, Conor.Dooley@microchip.com wrote:

On 10/11/2021 07:43, Krzysztof Kozlowski wrote:

quoted

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On 09/11/2021 14:36, Conor.Dooley@microchip.com wrote:

quoted

On 09/11/2021 12:56, Krzysztof Kozlowski wrote:

quoted

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On 09/11/2021 13:54, Conor.Dooley@microchip.com wrote:

quoted

On 08/11/2021 21:16, Krzysztof Kozlowski wrote:

quoted

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On 08/11/2021 16:05, conor.dooley@microchip.com wrote:

quoted

From: Conor Dooley <conor.dooley@microchip.com>

Add device tree bindings for the hardware rng device accessed via
the system services on the Microchip PolarFire SoC.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
    .../bindings/rng/microchip,mpfs-rng.yaml      | 31 +++++++++++++++++++
    1 file changed, 31 insertions(+)
    create mode 100644 Documentation/devicetree/bindings/rng/microchip,mpfs-rng.yaml

diff --git a/Documentation/devicetree/bindings/rng/microchip,mpfs-rng.yaml b/Documentation/devicetree/bindings/rng/microchip,mpfs-rng.yaml
new file mode 100644
index 000000000000..e8ecb3538a86
--- /dev/null
+++ b/Documentation/devicetree/bindings/rng/microchip,mpfs-rng.yaml

@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/rng/microchip,mpfs-rng.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Microchip MPFS random number generator
+
+maintainers:
+  - Conor Dooley <conor.dooley@microchip.com>
+
+properties:
+  compatible:
+    const: microchip,polarfire-soc-rng
+
+  syscontroller:
+    maxItems: 1
+    description: name of the system controller device node

There are several issues with this:
1. You need to describe the type.
2. Description is not helpful (just copying the name of property) and
actually misleading because you do not put there the name of device node.
3. What is it? Looks like syscon (or sometimes called sysreg). If yes,
please use existing syscon bindings.

1 & 2 - Correct, it is bad & I'll write a better description for it.
3 - Its a system controller implemented as a mailbox. The syscontroller
is the mailbox client, which the rng and generic drivers both use.

I understood that pointed device node is a mailbox, not this node. But
here, what is it here? How do you use it here?

The system controller is the means of access to the random number
generator. The phandle to the sys controller is provided here so that
the rng driver can locate the mailbox client through which it requests
random numbers.

I am asking this to understand whether there is a generic or existing
property which should be used instead.

If I understand correctly, the rng driver needs a mailbox client?

Correct, it needs one. Binding for that is here:
Documentation/devicetree/bindings/soc/microchip/microchip,polarfire-soc-sys-controller.yaml

The rng node and others should be a child of the sys controller node.

Rob