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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Fri, 19 Jan 2018 16:37:54 +0100
Message-ID: <CAMuHMdUqxuiTfM_m80F4XDVkZjx_XCsj_qXRehZxMcKjWhGQ_Q@mail.gmail.com>
Subject: Re: [PATCH v6 31/36] dt-bindings: nds32 CPU Bindings
To:     Greentime Hu <green.hu@gmail.com>
Cc:     Arnd Bergmann <arnd@arndb.de>, Greentime <greentime@andestech.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Jason Cooper <jason@lakedaemon.net>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Rob Herring <robh+dt@kernel.org>,
        Networking <netdev@vger.kernel.org>,
        Vincent Chen <deanbo422@gmail.com>,
        DTML <devicetree@vger.kernel.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        David Howells <dhowells@redhat.com>,
        Will Deacon <will.deacon@arm.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        linux-serial@vger.kernel.org,
        Linus Walleij <linus.walleij@linaro.org>,
        Mark Rutland <mark.rutland@arm.com>, Greg KH <greg@kroah.com>,
        Guo Ren <ren_guo@c-sky.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        David Miller <davem@davemloft.net>,
        Jonas Bonn <jonas@southpole.se>,
        Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
        Stafford Horne <shorne@gmail.com>,
        Vincent Chen <vincentc@andestech.com>,
        Rick Chen <rick@andestech.com>, Zong Li <zong@andestech.com>
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Hi Greentime,

On Fri, Jan 19, 2018 at 4:35 PM, Greentime Hu <green.hu@gmail.com> wrote:
> 2018-01-19 23:29 GMT+08:00 Geert Uytterhoeven <geert@linux-m68k.org>:
>> On Fri, Jan 19, 2018 at 4:18 PM, Greentime Hu <green.hu@gmail.com> wrote:
>>> 2018-01-19 22:52 GMT+08:00 Arnd Bergmann <arnd@arndb.de>:
>>>> On Fri, Jan 19, 2018 at 3:32 PM, Greentime Hu <green.hu@gmail.com> wrote:
>>>>> 2018-01-18 19:02 GMT+08:00 Arnd Bergmann <arnd@arndb.de>:
>>>>>> On Mon, Jan 15, 2018 at 6:53 AM, Greentime Hu <green.hu@gmail.com> wrote:
>>>>>>> From: Greentime Hu <greentime@andestech.com>
>>>>>>>
>>>>>>> This patch adds nds32 CPU binding documents.
>>>>>>>
>>>>>>> Signed-off-by: Vincent Chen <vincentc@andestech.com>
>>>>>>> Signed-off-by: Rick Chen <rick@andestech.com>
>>>>>>> Signed-off-by: Zong Li <zong@andestech.com>
>>>>>>> Signed-off-by: Greentime Hu <greentime@andestech.com>
>>>>>>> Reviewed-by: Rob Herring <robh@kernel.org>
>>>>>>> ---
>>>>>>>  Documentation/devicetree/bindings/nds32/cpus.txt |   37 ++++++++++++++++++++++
>>>>>>>  1 file changed, 37 insertions(+)
>>>>>>>  create mode 100644 Documentation/devicetree/bindings/nds32/cpus.txt
>>>>>>>
>>>>>>> diff --git a/Documentation/devicetree/bindings/nds32/cpus.txt b/Documentation/devicetree/bindings/nds32/cpus.txt
>>>>>>> new file mode 100644
>>>>>>> index 0000000..9a52937
>>>>>>> --- /dev/null
>>>>>>> +++ b/Documentation/devicetree/bindings/nds32/cpus.txt
>>>>>>> @@ -0,0 +1,37 @@
>>>>>>> +* Andestech Processor Binding
>>>>>>> +
>>>>>>> +This binding specifies what properties must be available in the device tree
>>>>>>> +representation of a Andestech Processor Core, which is the root node in the
>>>>>>> +tree.
>>>>>>> +
>>>>>>> +Required properties:
>>>>>>> +
>>>>>>> +       - compatible:
>>>>>>> +               Usage: required
>>>>>>> +               Value type: <string>
>>>>>>> +               Definition: should be one of:
>>>>>>> +                       "andestech,n13"
>>>>>>> +                       "andestech,n15"
>>>>>>> +                       "andestech,d15"
>>>>>>> +                       "andestech,n10"
>>>>>>> +                       "andestech,d10"
>>>>>>> +                       "andestech,nds32v3"
>>>>>>
>>>>>> Based on https://lkml.org/lkml/2017/11/27/1290, this should say that
>>>>>> the device tree should always list 'andestech,nds32v3' as the most
>>>>>> generic 'compatible' value and list exactly one of the others in
>>>>>> addition.
>>>>
>>>>> I will remove the others and just left "andestech,nds32v3" in here.
>>>>
>>>> No, is not what we want here, the CPU node should list exactly which core
>>>> is used, what we need in the description is a clarification that
>>>> andestech,nds32v3 must be used in addition to the more specific
>>>> string.
>>>
>>> Hi, Arnd:
>>>
>>> Sorry I still don't get your point. Do you mean we should always use
>>> compatible = "andestech,n13", "andestech,nds32v3";
>>> instead of
>>> compatible = "andestech,n13";
>>
>> Exactly. The first value is a device-specific compatible value, the second is
>> a generic fallback.
>>
>>> And I need to add the description in this document.
>>
>> Indeed. See for example
>> Documentation/devicetree/bindings/power/renesas,apmu.txt
>>
>> Thanks!
>
> Hi, Geert:
>
> Thank you and your example.
> I get it. I will update this document like this.
> - compatible: Should be "andestech,<core_name>", "andestech,nds32v3"
> as fallback.

And please keep a list of supported values of "andestech,<core_name>"
in the DT binding document, so checkpatch can validate compatible values.

Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds