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Subject: Re:Re: [PATCH v4 2/4] dt-bindings: mfd: sprd: Add bindings for ums512 global registers
From:   Stephen Boyd <sboyd@kernel.org>
Cc:     Chunyan Zhang <zhang.lyra@gmail.com>,
        Rob Herring <robh+dt@kernel.org>, linux-clk@vger.kernel.org,
        devicetree@vger.kernel.org, Baolin Wang <baolin.wang7@gmail.com>,
        Orson Zhai <orsonzhai@gmail.com>,
        Chunyan Zhang <chunyan.zhang@unisoc.com>,
        LKML <linux-kernel@vger.kernel.org>
To:     ChunyanZhang <zhanglyra@163.com>
Date:   Wed, 13 Oct 2021 23:38:42 -0700
Message-ID: <163419352215.936110.17102590465311356046@swboyd.mtv.corp.google.com>
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Quoting ChunyanZhang (2021-10-13 19:02:44)
> At 2021-10-14 09:51:25, "Stephen Boyd" <sboyd@kernel.org> wrote:
> >Quoting ChunyanZhang (2021-10-13 16:49:40)
> >> At 2021-10-14 06:04:32, "Stephen Boyd" <sboyd@kernel.org> wrote:
> >> >Quoting Chunyan Zhang (2021-09-22 23:41:35)
> >> >> diff --git a/Documentation/devicetree/bindings/mfd/sprd,ums512-glbr=
eg.yaml b/Documentation/devicetree/bindings/mfd/sprd,ums512-glbreg.yaml
> >> >> +
> >> >> +examples:
> >> >> +  - |
> >> >> +    ap_apb_regs: syscon@71000000 {
> >> >> +      compatible =3D "sprd,ums512-glbregs", "syscon", "simple-mfd";
> >> >> +      reg =3D <0x71000000 0x3000>;
> >> >> +      #address-cells =3D <1>;
> >> >> +      #size-cells =3D <1>;
> >> >> +      ranges =3D <0 0x71000000 0x3000>;
> >> >> +
> >> >> +      clock-controller@0 {
> >> >> +        compatible =3D "sprd,ums512-apahb-gate";
> >> >
> >> >Why is this a subnode of a syscon and simple-mfd? Why not put the>clo=
ck-controller@71000000 directly onto the bus? Does making it a child
> >> >node help somehow?
> >>=20
> >> These clocks are at the same register range with global registers. I o=
riginally put them directly onto the bus indeed when submitting the patches=
 for SC9863A clocks last year, and it had a private property named 'sprd,sy=
scon' which could provide regmap for these clocks.
> >>=20
> >> 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?
>=20
> Yes, shared with more than one devices which basically are multimedia dev=
ices. You may noticed that these are all gate clocks which are in the globa=
l registers ranges and are used to controll the enable status of some devic=
es or some part of devices.
>=20

Where does the multimedia device address space start? I see 0x71000000
to 0x71002000 is for the clock-controller. Is the multimedia device at
0x71002000 to 0x71003000? If so they're next to each other but not
sharing the same register space. Is ap_apb_regs more like a soft macro
that combines a few clks with some multimedia device?