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Date:   Fri, 20 Mar 2020 11:50:36 +0200
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Rob Herring <robh@kernel.org>
Cc:     linux-kernel@vger.kernel.org,
        Kishon Vijay Abraham I <kishon@ti.com>,
        Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>,
        Michal Simek <michal.simek@xilinx.com>,
        devicetree@vger.kernel.org
Subject: Re: [PATCH v6 1/3] dt-bindings: phy: Add DT bindings for Xilinx
 ZynqMP PSGTR PHY
Message-ID: <20200320095036.GA5193@pendragon.ideasonboard.com>
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 <20200311103252.17514-2-laurent.pinchart@ideasonboard.com>
 <20200320023520.GA18490@bogus>
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Hi Rob,

On Thu, Mar 19, 2020 at 08:35:20PM -0600, Rob Herring wrote:
> On Wed, Mar 11, 2020 at 12:32:50PM +0200, Laurent Pinchart wrote:
> > From: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
> > 
> > Add DT bindings for the Xilinx ZynqMP PHY. ZynqMP SoCs have a High Speed
> > Processing System Gigabit Transceiver which provides PHY capabilities to
> > USB, SATA, PCIE, Display Port and Ehernet SGMII controllers.
> > 
> > Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
> > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > ---
> > Changes since v5:
> > 
> > - Document clocks and clock-names properties
> > - Document resets and reset-names properties
> > - Replace subnodes with an additional entry in the PHY cells
> > - Drop lane frequency PHY cell, replaced by reference clock phandle
> > - Convert bindings to YAML
> > - Reword the subject line
> > - Drop Rob's R-b as the bindings have significantly changed
> > - Drop resets and reset-names properties
> > ---
> >  .../bindings/phy/xlnx,zynqmp-psgtr.yaml       | 104 ++++++++++++++++++
> >  include/dt-bindings/phy/phy.h                 |   1 +
> >  2 files changed, 105 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/phy/xlnx,zynqmp-psgtr.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/phy/xlnx,zynqmp-psgtr.yaml b/Documentation/devicetree/bindings/phy/xlnx,zynqmp-psgtr.yaml
> > new file mode 100644
> > index 000000000000..9948e4a60e45
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/phy/xlnx,zynqmp-psgtr.yaml
> > @@ -0,0 +1,104 @@
> > +# SPDX-License-Identifier: GPL-2.0
> 
> For new bindings:
> 
> (GPL-2.0-only OR BSD-2-Clause)
> 
> Though I guess Anurag needs to agree.

There's an ongoing similar discussion regarding the DPSUB (DRM/KMS)
bindings. Hyun is checking with the Xilinx legal department. If they
agree, I'll change the license here, otherwise I'll keep it as-is.

> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/phy/xlnx,zynqmp-psgtr.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Xilinx ZynqMP Gigabit Transceiver PHY Device Tree Bindings
> > +
> > +maintainers:
> > +  - Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > +
> > +description: |
> > +  This binding describes the Xilinx ZynqMP Gigabit Transceiver (GTR) PHY. The
> > +  GTR provides four lanes and is used by USB, SATA, PCIE, Display port and
> > +  Ethernet SGMII controllers.
> > +
> > +properties:
> > +  "#phy-cells":
> > +    const: 4
> > +    description: |
> > +      The cells contain the following arguments.
> > +
> > +      - description: The GTR lane
> > +        minimum: 0
> > +        maximum: 3
> > +      - description: The PHY type
> > +        enum:
> > +          - PHY_TYPE_DP
> > +          - PHY_TYPE_PCIE
> > +          - PHY_TYPE_SATA
> > +          - PHY_TYPE_SGMII
> > +          - PHY_TYPE_USB
> > +      - description: The PHY instance
> > +        minimum: 0
> > +        maximum: 1 # for DP, SATA or USB
> > +        maximum: 3 # for PCIE or SGMII
> > +      - description: The reference clock number
> > +        minimum: 0
> > +        maximum: 3
> 
> Humm, interesting almost json-schema. I guess it's fine as-is.
> 
> I would like to figure out how to apply a schema like this to the 
> consumer nodes. We'd have to look up the phandle, get that node's 
> compatible, find the provider's schema, find #.*-cells property, and 
> extract a schema from it. Actually, doesn't sound too hard.

That would be nice :-)

> > +
> > +  compatible:
> > +    enum:
> > +      - xlnx,zynqmp-psgtr-v1.1
> > +      - xlnx,zynqmp-psgtr
> > +
> > +  clocks:
> > +    minItems: 1
> > +    maxItems: 4
> > +    description: |
> > +      Clock for each PS_MGTREFCLK[0-3] reference clock input. Unconnected
> > +      inputs shall not have an entry.
> > +
> > +  clock-names:
> > +    minItems: 1
> > +    maxItems: 4
> > +    items:
> > +      pattern: "^ref[0-3]$"
> > +
> > +  reg:
> > +    items:
> > +      - description: SERDES registers block
> > +      - description: SIOU registers block
> > +
> > +  reg-names:
> > +    items:
> > +      - const: serdes
> > +      - const: siou
> > +
> > +required:
> > +  - "#phy-cells"
> > +  - compatible
> > +  - reg
> > +  - reg-names
> > +
> > +if:
> > +  properties:
> > +    compatible:
> > +      const: xlnx,zynqmp-psgtr
> > +
> > +then:
> > +  properties:
> > +    xlnx,tx-termination-fix:
> > +      description: |
> > +        Include this for fixing functional issue with the TX termination
> > +        resistance in GT, which can be out of spec for the XCZU9EG silicon
> > +        version.
> > +      type: boolean
> > +
> > +additionalProperties: false
> 
> This won't work with 'xlnx,tx-termination-fix'. You need to move it to 
> the main properties section and then do:
> 
> if:
>   properties:
>     compatible:
>       const: xlnx,zynqmp-psgtr-v1.1

It doesn't make a big difference as only two compatible values are
allowed, but is there a way to express the condition the other way
around, if (compatible != "xlnx,zynqmp-psgtr") ?

> 
> then:
>   properties:
>     xlnx,tx-termination-fix: false

This works.

> I think this would also work:
> 
>   not:
>     required:
>       - xlnx,tx-termination-fix

I've tested it and it works, but I'm not sure why, given that the
property isn't required required in the first place. Could you enlighten
me ?

> > +
> > +examples:
> > +  - |
> > +    phy: phy@fd400000 {
> > +      compatible = "xlnx,zynqmp-psgtr-v1.1";
> > +      reg = <0x0 0xfd400000 0x0 0x40000>,
> > +            <0x0 0xfd3d0000 0x0 0x1000>;
> > +      reg-names = "serdes", "siou";
> > +      clocks = <&refclks 3>, <&refclks 2>, <&refclks 0>;
> > +      clock-names = "ref1", "ref2", "ref3";
> > +      #phy-cells = <4>;
> > +      status = "okay";
> 
> Drop status in examples.

OK.

> > +    };
> > +
> > +...
> > diff --git a/include/dt-bindings/phy/phy.h b/include/dt-bindings/phy/phy.h
> > index 1f3f866fae7b..f6bc83b66ae9 100644
> > --- a/include/dt-bindings/phy/phy.h
> > +++ b/include/dt-bindings/phy/phy.h
> > @@ -17,5 +17,6 @@
> >  #define PHY_TYPE_USB3		4
> >  #define PHY_TYPE_UFS		5
> >  #define PHY_TYPE_DP		6
> > +#define PHY_TYPE_SGMII		7
> >  
> >  #endif /* _DT_BINDINGS_PHY */

-- 
Regards,

Laurent Pinchart