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

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Message-ID: <ea871add-bddc-c4ae-ac9d-e86b4fad5a02@microchip.com>
Date:   Tue, 9 Nov 2021 13:36:04 +0000
From:   <Conor.Dooley@...rochip.com>
To:     <krzysztof.kozlowski@...onical.com>
CC:     <broonie@...nel.org>, <aou@...s.berkeley.edu>,
        <robh+dt@...nel.org>, <linus.walleij@...aro.org>,
        <bgolaszewski@...libre.com>, <palmer@...belt.com>,
        <paul.walmsley@...ive.com>, <jassisinghbrar@...il.com>,
        <atish.patra@....com>, <Daire.McNamara@...rochip.com>,
        <Lewis.Hanly@...rochip.com>, <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <geert@...ux-m68k.org>,
        <linux-gpio@...r.kernel.org>, <linux-riscv@...ts.infradead.org>,
        <linux-crypto@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <bin.meng@...driver.com>, <linux-i2c@...r.kernel.org>,
        <alexandre.belloni@...tlin.com>, <Ivan.Griffin@...rochip.com>,
        <linux-rtc@...r.kernel.org>, <linux-spi@...r.kernel.org>,
        <a.zummo@...ertech.it>, <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 06/13] dt-bindings: rng: add bindings for microchip mpfs
 rng

On 09/11/2021 12:56, Krzysztof Kozlowski wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On 09/11/2021 13:54, Conor.Dooley@...rochip.com wrote:
>> On 08/11/2021 21:16, Krzysztof Kozlowski wrote:
>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>
>>> On 08/11/2021 16:05, conor.dooley@...rochip.com wrote:
>>>> From: Conor Dooley <conor.dooley@...rochip.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@...rochip.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@...rochip.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'm not quite sure that I am answering the question you are asking though.
> 
> Best regards,
> Krzysztof
>