Re: [PATCH v3 2/5] dt: bindings: add mt7621-clk device tree binding documentation

[Sergio Paracuellos <sergio.paracuellos@gmail.com>]

On Sat, Nov 21, 2020 at 3:50 PM Sergio Paracuellos
<sergio.paracuellos@gmail.com> wrote:
>
> Hi Rob,
>
> Thanks for the review.
>
> On Sat, Nov 21, 2020 at 2:34 PM Rob Herring <robh@kernel.org> wrote:
> >
> > On Fri, Nov 13, 2020 at 04:46:29PM +0100, Sergio Paracuellos wrote:
> > > Adds device tree binding documentation for clocks in the
> > > MT7621 SOC.
> > >
> > > Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
> > > ---
> > >  .../bindings/clock/mediatek,mt7621-clk.yaml   | 61 +++++++++++++++++++
> > >  1 file changed, 61 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/clock/mediatek,mt7621-clk.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/clock/mediatek,mt7621-clk.yaml b/Documentation/devicetree/bindings/clock/mediatek,mt7621-clk.yaml
> > > new file mode 100644
> > > index 000000000000..363bd9880e29
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/clock/mediatek,mt7621-clk.yaml
> > > @@ -0,0 +1,61 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/clock/mediatek,mt7621-clk.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: MT7621 Clock Device Tree Bindings
> > > +
> > > +maintainers:
> > > +  - Sergio Paracuellos <sergio.paracuellos@gmail.com>
> > > +
> > > +description: |
> > > +  The MT7621 has a PLL controller from where the cpu clock is provided
> > > +  as well as derived clocks for the bus and the peripherals. It also
> > > +  can gate SoC device clocks.
> > > +
> > > +  Each clock is assigned an identifier and client nodes use this identifier
> > > +  to specify the clock which they consume.
> > > +
> > > +  All these identifiers could be found in:
> > > +  [1]: <include/dt-bindings/clock/mt7621-clk.h>.
> > > +
> > > +properties:
> > > +  compatible:
> > > +    const: mediatek,mt7621-clk
> > > +
> > > +  ralink,sysctl:
> > > +    $ref: /schemas/types.yaml#/definitions/phandle
> > > +    description:
> > > +      phandle to the syscon which is in the same address area with syscon
> > > +      device.
> > > +
> > > +  "#clock-cells":
> > > +    description:
> > > +      The first cell indicates the clock gate number, see [1] for available
> > > +      clocks.
> > > +    const: 1
> > > +
> > > +  clock-output-names:
> > > +    maxItems: 8
> > > +
> > > +required:
> > > +  - compatible
> > > +  - ralink,sysctl
> > > +  - '#clock-cells'
> > > +  - clock-output-names
> > > +
> > > +additionalProperties: false
> > > +
> > > +examples:
> > > +  - |
> > > +    #include <dt-bindings/clock/mt7621-clk.h>
> > > +
> > > +    pll {
> > > +      compatible = "mediatek,mt7621-clk";
> > > +      ralink,sysctl = <&sysc>;
> >
> > If this is the only control interface, then make this a child of 'sysc'.
> > And use 'reg' if there's a dedicated range of registers.
>
> This is the only one now in the device tree which is still in staging
> but there are several places where this sys control registers are
> accessed from. In the case of the clocks we need:
>
> #define SYSC_REG_SYSTEM_CONFIG0         0x10
> #define SYSC_REG_SYSTEM_CONFIG1         0x14
> #define SYSC_REG_CLKCFG0                0x2c
> #define SYSC_REG_CLKCFG1                0x30
> #define SYSC_REG_CUR_CLK_STS            0x44
>
> where there is not a range as it is but several different registers
> from where we need to read or write things. I wrote the driver using
> syscon and regmap because I thought in that way it might be more
> maintainable but this architecture also has operations to read and
> write registers from sysc and not using regmap at all. This operations
> are defined in arch/mips/include/asm/mach-ralink/ralink_regs.h. But
> because this sysc is currently mapped I cannot request its registers
> using reg in the device tree. If you prefer me to avoid the use of
> this syscon and regmap and use operations defined in ralink_regs.h,
> this will become in a node without "regs" or  "ralink,sysctl"
> property:
>
> pll {
>     compatible = "mediatek,mt7621-clk";
>     #clock-cells = <1>;
>     clock-output-names = "xtal", "cpu", "bus",
>                       "50m", "125m", "150m",
>                        "250m", "270m";
> };
>
> What should I do then?

Ok, I think I understand now what you are saying. You meant just move
this as a child if 'sysc' and
avoid the phandle:

    sysc: sysc@0 {
            compatible = "mtk,mt7621-sysc", "syscon";
            reg = <0x0 0x100>;

            pll: pll {
                compatible = "mediatek,mt7621-clk";
                #clock-cells = <1>;
                clock-output-names = "xtal", "cpu", "bus",
                                  "50m", "125m", "150m",
                                 "250m", "270m";
            };
        };

And because there is not a range of registers 'reg' property is not
needed, right?

And in the driver side make use of 'syscon_node_to_regmap(node->parent)' instead
of 'syscon_regmap_lookup_by_phandle(node, "ralink,sysctl")'.

Ok, thanks for the clarification. Will change when v4 is sent.

Best regards,
    Sergio Paracuellos
>
> Best regards,
>     Sergio Paracuellos
>
> >
> > > +      #clock-cells = <1>;
> > > +      clock-output-names = "xtal", "cpu", "bus",
> > > +                           "50m", "125m", "150m",
> > > +                           "250m", "270m";
> > > +    };
> > > --
> > > 2.25.1
> > >