linux-kernel - Re:Re: [PATCH v4 2/4] dt-bindings: mfd: sprd: Add bindings for ums512 global registers

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Date:   Thu, 14 Oct 2021 10:02:44 +0800 (CST)
From:   ChunyanZhang <zhanglyra@....com>
To:     "Stephen Boyd" <sboyd@...nel.org>
Cc:     "Chunyan Zhang" <zhang.lyra@...il.com>,
        "Rob Herring" <robh+dt@...nel.org>, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, "Baolin Wang" <baolin.wang7@...il.com>,
        "Orson Zhai" <orsonzhai@...il.com>,
        "Chunyan Zhang" <chunyan.zhang@...soc.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re:Re: [PATCH v4 2/4] dt-bindings: mfd: sprd: Add bindings for
 ums512 global registers

At 2021-10-14 09:51:25, "Stephen Boyd" <sboyd@...nel.org> wrote:
>Quoting ChunyanZhang (2021-10-13 16:49:40)
>> At 2021-10-14 06:04:32, "Stephen Boyd" <sboyd@...nel.org> wrote:
>> >Quoting Chunyan Zhang (2021-09-22 23:41:35)
>> >> diff --git a/Documentation/devicetree/bindings/mfd/sprd,ums512-glbreg.yaml b/Documentation/devicetree/bindings/mfd/sprd,ums512-glbreg.yaml
>> >> +
>> >> +examples:
>> >> +  - |
>> >> +    ap_apb_regs: syscon@...00000 {
>> >> +      compatible = "sprd,ums512-glbregs", "syscon", "simple-mfd";
>> >> +      reg = <0x71000000 0x3000>;
>> >> +      #address-cells = <1>;
>> >> +      #size-cells = <1>;
>> >> +      ranges = <0 0x71000000 0x3000>;
>> >> +
>> >> +      clock-controller@0 {
>> >> +        compatible = "sprd,ums512-apahb-gate";
>> >
>> >Why is this a subnode of a syscon and simple-mfd? Why not put the>clock-controller@...00000 directly onto the bus? Does making it a child
>> >node help somehow?
>> 
>> These clocks are at the same register range with global registers. I originally put them directly onto the bus indeed when submitting the patches for SC9863A clocks last year, and it had a private property named 'sprd,syscon' which could provide regmap for these clocks.
>> 
>> Rob suggested [1] us to make them a child of the syscon, and would not need the private property 'sprd, syscon' then.
>
>Why do you need to use a syscon? Are the registers shared with some
>other driver?

Yes, shared with more than one devices which basically are multimedia devices. You may noticed that these are all gate clocks which are in the global registers ranges and are used to controll the enable status of some devices or some part of devices.

>
>2019 was two years ago...

Humm... yes, submitted that patch set from 2019 to 2020 :)