Re: [PATCH v2 5/5] dt-bindings: net: ipq4019-mdio: Document ipq5332 platform

[Conor Dooley <conor@kernel.org>]

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On Wed, Dec 13, 2023 at 04:26:56PM +0800, Jie Luo wrote:
> 
> 
> On 12/13/2023 12:06 AM, Conor Dooley wrote:
> > On Tue, Dec 12, 2023 at 07:51:50PM +0800, Luo Jie wrote:
> > > Update the yaml file for the new DTS properties.
> > > 
> > > 1. cmn-reference-clock for the CMN PLL source clock select.
> > > 2. clock-frequency for MDIO clock frequency config.
> > > 3. add uniphy AHB & SYS GCC clocks.
> > > 4. add reset-gpios for MDIO bus level reset.
> > > 
> > > Signed-off-by: Luo Jie <quic_luoj@quicinc.com>
> > > ---
> > >   .../bindings/net/qcom,ipq4019-mdio.yaml       | 157 +++++++++++++++++-
> > >   1 file changed, 153 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/net/qcom,ipq4019-mdio.yaml b/Documentation/devicetree/bindings/net/qcom,ipq4019-mdio.yaml
> > > index 3407e909e8a7..9546a6ad7841 100644
> > > --- a/Documentation/devicetree/bindings/net/qcom,ipq4019-mdio.yaml
> > > +++ b/Documentation/devicetree/bindings/net/qcom,ipq4019-mdio.yaml
> > > @@ -20,6 +20,8 @@ properties:
> > >             - enum:
> > >                 - qcom,ipq6018-mdio
> > >                 - qcom,ipq8074-mdio
> > > +              - qcom,ipq9574-mdio
> > > +              - qcom,ipq5332-mdio
> > >             - const: qcom,ipq4019-mdio
> > >     "#address-cells":
> > > @@ -30,19 +32,71 @@ properties:
> > >     reg:
> > >       minItems: 1
> > > -    maxItems: 2
> > > +    maxItems: 5
> > >       description:
> > > -      the first Address and length of the register set for the MDIO controller.
> > > -      the second Address and length of the register for ethernet LDO, this second
> > > -      address range is only required by the platform IPQ50xx.
> > > +      the first Address and length of the register set for the MDIO controller,
> > > +      the optional second, third and fourth address and length of the register
> > > +      for ethernet LDO, these three address range are required by the platform
> > > +      IPQ50xx/IPQ5332/IPQ9574, the last address and length is for the CMN clock
> > > +      to select the reference clock.
> > > +
> > > +  reg-names:
> > > +    minItems: 1
> > > +    maxItems: 5
> > >     clocks:
> > > +    minItems: 1
> > >       items:
> > >         - description: MDIO clock source frequency fixed to 100MHZ
> > > +      - description: UNIPHY0 AHB clock source frequency fixed to 100MHZ
> > > +      - description: UNIPHY1 AHB clock source frequency fixed to 100MHZ
> > > +      - description: UNIPHY0 SYS clock source frequency fixed to 24MHZ
> > > +      - description: UNIPHY1 SYS clock source frequency fixed to 24MHZ
> > >     clock-names:
> > > +    minItems: 1
> > >       items:
> > >         - const: gcc_mdio_ahb_clk
> > > +      - const: gcc_uniphy0_ahb_clk
> > > +      - const: gcc_uniphy1_ahb_clk
> > > +      - const: gcc_uniphy0_sys_clk
> > > +      - const: gcc_uniphy1_sys_clk
> > 
> > > +  cmn-reference-clock:
> > > +    oneOf:
> > > +      - items:
> > > +          - enum:
> > > +              - 0   # CMN PLL reference internal 48MHZ
> > > +              - 1   # CMN PLL reference external 25MHZ
> > > +              - 2   # CMN PLL reference external 31250KHZ
> > > +              - 3   # CMN PLL reference external 40MHZ
> > > +              - 4   # CMN PLL reference external 48MHZ
> > > +              - 5   # CMN PLL reference external 50MHZ
> > > +              - 6   # CMN PLL reference internal 96MHZ
> > 
> > Why is this not represented by an element of the clocks property?
> 
> This property is for the reference clock source selection of CMN PLL,
> CMN PLL generates the different clock rates for the different Ethernet
> blocks, this CMN PLL configuration is not located in the GCC, so the
> clock framework can't be used, which is the general hardware register
> instead of RCG register for GCC.

I don't see how the clock being provided by the "GCC" (whatever that is)
or by some other clock controller or fixed clock makes a difference.
Why can't the other clock provider be represented in the devicetree?

> > > +  clock-frequency:
> > > +    oneOf:
> > > +      - items:
> > > +          - enum:
> > > +              - 12500000
> > > +              - 6250000
> > > +              - 3125000
> > > +              - 1562500
> > > +              - 781250
> > > +              - 390625
> > > +    description:
> > > +      The MDIO bus clock that must be output by the MDIO bus hardware,
> > > +      only the listed frequecies above can be configured, other frequency
> > > +      will cause malfunction. If absent, the default hardware value is used.
> > 
> > Likewise.
> > 
> > Your commit message contains a bullet point list of what you are doing,
> > but there's no explanation here for why custom properties are required
> > to provide clock information.

> This property clock-frequency is optional to configure the MDIO working
> clock rate, and this is the MDIO general DT property, since the hardware
> default clock rate is 390625HZ, there is requirement for higher clock rate
> in the normal working case, i will update this information in the
> next patch set.

I'm just realising that this particular one is not a custom property,
the unusual `oneOf: - items: - enum:` structure here threw me. This can
just be
  clock-frequency:
    enum:
      - 12500000
      - 6250000
      - 3125000
      - 1562500
      - 781250
      - 390625

but you're missing a default, given your commit about the last element
in that list being one.

Thanks,
Conor.

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