linux-kernel - Re: [PATCH v4 03/17] dt-bindings: PCI: dwc: Add phys/phy-names common properties

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Date:   Mon, 8 Aug 2022 13:36:10 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Frank Li <Frank.Li@....com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 03/17] dt-bindings: PCI: dwc: Add phys/phy-names
 common properties

On Mon, Aug 01, 2022 at 11:56:36AM -0600, Rob Herring wrote:
> On Thu, Jul 28, 2022 at 05:34:13PM +0300, Serge Semin wrote:
> > It's normal to have the DW PCIe RP/EP DT-nodes equipped with the explicit
> > PHY phandle references. There can be up to 16 PHYs attach in accordance
> > with the maximum number of supported PCIe lanes. Let's extend the common
> > DW PCIe controller schema with the 'phys' and 'phy-names' properties
> > definition. The PHY names are defined with the regexp pattern
> > '^pcie([0-9]+|-?phy[0-9]*)?$' so to match the names currently supported by
> > the DW PCIe platform drivers ("pcie": meson; "pciephy": qcom, imx6;
> > "pcie-phy": uniphier, rockchip, spear13xx; "pcie": intel-gw; "pcie-phy%d":
> > keystone, dra7xx; "pcie": histb, etc). Though the "pcie%d" format would
> > the most preferable in this case.
> 

> No phy-names is my preference. Some string plus an index is utterly 
> pointless. Oh well...

Mine too, but we have no choice in this case since the named
PHY-properties support has already been advertised by the platform
drivers. This patch just provides the bindings for them. Just note
the string patterns have been designed in a way to match these bindings.

Anyway thanks for telling about the preferred option. Keeping that in
mind I won't have doubts what approach to select for the new
driver/bindings development.

> 
> > 
> > Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> > 
> > ---
> > 
> > Changelog v3:
> > - This is a new patch unpinned from the next one:
> >   https://lore.kernel.org/linux-pci/20220503214638.1895-2-Sergey.Semin@baikalelectronics.ru/
> >   by the Rob' request. (@Rob)
> > ---
> >  .../bindings/pci/snps,dw-pcie-common.yaml         | 15 +++++++++++++++
> >  .../devicetree/bindings/pci/snps,dw-pcie-ep.yaml  |  3 +++
> >  .../devicetree/bindings/pci/snps,dw-pcie.yaml     |  3 +++
> >  3 files changed, 21 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/pci/snps,dw-pcie-common.yaml b/Documentation/devicetree/bindings/pci/snps,dw-pcie-common.yaml
> > index 3e992b653d12..627a5d6625ba 100644
> > --- a/Documentation/devicetree/bindings/pci/snps,dw-pcie-common.yaml
> > +++ b/Documentation/devicetree/bindings/pci/snps,dw-pcie-common.yaml
> > @@ -17,6 +17,21 @@ description:
> >  select: false
> >  
> >  properties:
> > +  phys:
> > +    description:
> > +      There can be up to the number of possible lanes PHYs specified.
> 

> This needs something about being in order of lane number.

Ok.

> 
> > +      Obviously each specified PHY is supposed to be able to work in the
> > +      PCIe mode with a speed implied by the DWC PCIe controller it is
> > +      attached to.
> > +    minItems: 1
> > +    maxItems: 16
> > +
> > +  phy-names:
> > +    minItems: 1
> > +    maxItems: 16
> > +    items:
> > +      pattern: '^pcie([0-9]+|-?phy[0-9]*)?$'
> 

> Please comment here that pcie[0-9] is the preferred form.

What about a bit more sophisticated update?
phy-names:
  minItems: 1
  maxItems: 16
  oneOf:
    - items:
        pattern: '^pcie[0-9]+$'
    - deprecated: true
      items:
        pattern: '^pcie(-?phy[0-9]*)?$'

-Sergey

> 
> Rob