linux-kernel - Re: [PATCH 1/3] dt-bindings: Add support for Broadcom USB pin map driver

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Message-ID: <CAL_JsqLvDq1L1BZKfgobfhe7UEqbkGtXXfHzUwfo36m4MCARhw@mail.gmail.com>
Date:   Tue, 25 Aug 2020 09:46:08 -0600
From:   Rob Herring <robh@...nel.org>
To:     Alan Cooper <alcooperx@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     ": Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>,
        DTML <devicetree@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "moderated list:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        USB list <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 1/3] dt-bindings: Add support for Broadcom USB pin map driver

+Linus W

On Tue, Aug 25, 2020 at 6:26 AM Alan Cooper <alcooperx@...il.com> wrote:
>
> On Mon, Aug 24, 2020 at 7:30 PM Rob Herring <robh@...nel.org> wrote:
> >
> > On Wed, Aug 12, 2020 at 04:20:16PM -0400, Al Cooper wrote:
> > > Add DT bindings for the Broadcom USB pin map driver. This driver allows
> > > some USB input and output signals to be mapped to any GPIO instead
> > > of the normal dedicated pins to/from the XHCI controller.
> >
> > Is this a driver or h/w block because bindings are for h/w blocks?
>
> This is a hardware block. I'll remove "driver" from the description.

Another question, this kind of looks like a pin mux controller. Is
that not a fit for this? If not, why?

> > > Signed-off-by: Al Cooper <alcooperx@...il.com>
> > > ---
> > >  .../bindings/usb/brcm,usb-pinmap.yaml         | 63 +++++++++++++++++++
> > >  1 file changed, 63 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/usb/brcm,usb-pinmap.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/usb/brcm,usb-pinmap.yaml b/Documentation/devicetree/bindings/usb/brcm,usb-pinmap.yaml
> > > new file mode 100644
> > > index 000000000000..19cf6ad36373
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/usb/brcm,usb-pinmap.yaml
> > > @@ -0,0 +1,63 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/usb/brcm,usb-pinmap.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Broadcom USB pin map Controller Device Tree Bindings
> > > +
> > > +maintainers:
> > > +  - Al Cooper <alcooperx@...il.com>
> > > +
> > > +properties:
> > > +  compatible:
> > > +      items:
> > > +          - const: brcm,usb-pinmap
> >
> > 2 space indentation please.
>
> Fixed.
>
> >
> > > +
> > > +  reg:
> > > +    maxItems: 1
> > > +
> > > +  interrupts:
> > > +    maxItems: 1
> > > +    description: Must be defined if any out-gpios are specified.
> >
> > 'dependencies' can express this in schema.
>
> Okay.
>
> >
> > > +
> > > +  in-gpios:
> > > +    description: Array of one or more GPIO pins used for input signals.
> >
> > You need to define how many GPIOs are valid.
>
> I tried to avoid doing this because there is a possibility that future
> chips will have a few more signals added and the driver was written so
> new signals can be added entirely in device tree without any changes
> to the driver. If this is unacceptable, I can add the current max in
> and out valid gpios.

A 'should be enough for a while' value is fine. The driver doesn't
have to have a max. I'd expect the binding to be updated for new SoCs
anyways.

> >
> > > +
> > > +  in-names:
> > > +    description: Array of input signal names, one per gpio in in-gpios.
> >
> > No, this isn't how we name GPIOs. The part before '-gpios' is how.
>
> This is the meant to be a description of how each gpio is being used
> to help with error messages in the driver.
> What if I use "brcmstb,in-functions" instead?

'brcmstb' is not a vendor. But brcm,in-functions is fine.

> > > +
> > > +  in-masks:
> > > +    description: Array of enable and mask pairs, one per gpio in-gpios.
> >
> > Needs a vendor prefix.
>
> I'll change it to "brcmstb,in-masks"
>
> >
> > > +
> > > +  out-gpios:
> > > +    description: Array of one or more GPIO pins used for output signals.
> > > +
> > > +  out-names:
> > > +    description: Array of output signal names, one per gpio in out-gpios.
> > > +
> > > +  out-masks:
> > > +    description: Array of enable, value, changed and clear masks, one
> > > +      per gpio in out-gpios.
> > > +
> > > +required:
> > > +  - compatible
> > > +  - reg
> > > +
> > > +additionalProperties: false
> > > +
> > > +examples:
> > > +  - |
> > > +    usb_pinmap: usb-pinmap@...00d0 {
> > > +        compatible = "brcm,usb-pinmap";
> > > +        reg = <0x22000d0 0x4>;
> > > +        in-gpios = <&gpio 18 0>, <&gpio 19 0>;
> > > +        in-names = "VBUS", "PWRFLT";
> > > +        in-masks = <0x8000 0x40000 0x10000 0x80000>;
> > > +        out-gpios = <&gpio 20 0>;
> > > +        out-names = "PWRON";
> > > +        out-masks = <0x20000 0x800000 0x400000 0x200000>;
> > > +        interrupts = <0x0 0xb2 0x4>;
> > > +    };
> > > +
> > > +...
> > > --
> > > 2.17.1
> > >