linux-kernel - Re: [PATCH v2 1/3] dt-bindings: arm: amlogic: Add SoC information bindings

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Message-ID: <CAL_JsqKGuq2sW1m+JpkYgN-aBj537aNfZn2wb_pnU+FLEa_igg@mail.gmail.com>
Date:   Fri, 9 Jun 2017 10:46:37 -0500
From:   Rob Herring <robh@...nel.org>
To:     Neil Armstrong <narmstrong@...libre.com>
Cc:     Kevin Hilman <khilman@...libre.com>,
        Carlo Caione <carlo@...one.org>,
        linux-amlogic@...ts.infradead.org,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 1/3] dt-bindings: arm: amlogic: Add SoC information bindings

On Fri, Jun 9, 2017 at 8:58 AM, Neil Armstrong <narmstrong@...libre.com> wrote:
> On 06/09/2017 03:37 PM, Rob Herring wrote:
>> On Tue, Jun 06, 2017 at 11:45:38AM +0200, Neil Armstrong wrote:
>>> Add bindings for the SoC information register of the Amlogic SoCs.
>>>
>>> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
>>> ---
>>>  Documentation/devicetree/bindings/arm/amlogic.txt | 32 +++++++++++++++++++++++
>>>  1 file changed, 32 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/arm/amlogic.txt b/Documentation/devicetree/bindings/arm/amlogic.txt
>>> index 5c01e65..ae3e8ed 100644
>>> --- a/Documentation/devicetree/bindings/arm/amlogic.txt
>>> +++ b/Documentation/devicetree/bindings/arm/amlogic.txt
>>> @@ -60,3 +60,35 @@ Board compatible values (alphabetically, grouped by SoC):
>>>    - "amlogic,q201" (Meson gxm s912)
>>>    - "kingnovel,r-box-pro" (Meson gxm S912)
>>>    - "nexbox,a1" (Meson gxm s912)
>>> +
>>> +Amlogic Meson Firmware registers Interface
>>> +------------------------------------------
>>> +
>>> +The Meson SoCs have a register bank with status and data shared with the
>>> +secure firmware.
>>> +
>>> +Required properties:
>>> + - compatible: For Meson GX SoCs, must be "amlogic,meson-gx-ao-secure", "syscon", "simple-mfd"
>>> +
>>> +Sub-nodes should indentify components of this register interface :
>>> +
>>> +Meson GX SoC Information
>>> +------------------------
>>> +A firmware register encodes the SoC type, package and revision information on
>>> +the Meson GX SoCs.
>>> +If present, a device node for this register should be added.
>>> +
>>> +Required properties:
>>> +  - compatible: For Meson GX SoCs, must be "amlogic,meson-gx-chipid".
>>> +
>>> +Example
>>> +-------
>>> +
>>> +ao-secure@140 {
>>> +    compatible = "amlogic,meson-gx-ao-secure", "syscon", "simple-mfd";
>>> +    reg = <0x0 0x140 0x0 0x140>;
>>> +
>>> +    chipid {
>>> +            compatible = "amlogic,meson-gx-chipid";
>>
>> No registers for this block? If not, this node is pointless.
>> "amlogic,meson-gx-ao-secure" should be specific enough to determine if
>> you have this block or not and the driver for it can create a device if
>> the OS needs it.
>>
>> Rob
>>
>
> Well OK, but since it's a firmware interface, it can be handy to list the
> possible capabilities, not especially tied to a driver.

A "has-chip-id;" property would do that.

It would be better to just be very explicit about what version of
firmware you have and that can imply anything and everything you need
to know about the firmware without needing to up date the dtb every
time you need to provide a new (to Linux) firmware capability.

Rob