[RFC PATH 1/2] dt-bindings: gpio: add starfive,jh7100-gpio bindings

[Drew Fustini]

On Fri, Jul 02, 2021 at 11:03:56PM +0200, Geert Uytterhoeven wrote:
> Hi Drew,
> 
> On Fri, Jul 2, 2021 at 10:56 PM Drew Fustini <drew at beagleboard.org> wrote:
> > On Thu, Jul 01, 2021 at 10:34:56AM +0200, Geert Uytterhoeven wrote:
> > > On Thu, Jul 1, 2021 at 2:22 AM Drew Fustini <drew at beagleboard.org> wrote:
> > > > Add bindings for the GPIO controller in the StarFive JH7100 SoC [1].
> > > >
> > > > [1] https://github.com/starfive-tech/beaglev_doc
> > > >
> > > > Signed-off-by: Drew Fustini <drew at beagleboard.org>
> > > > Signed-off-by: Huan Feng <huan.feng at starfivetech.com>
> > >
> > > Thanks for your patch!
> > >
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/gpio/starfive,jh7100-gpio.yaml
> > > > @@ -0,0 +1,60 @@
> > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > > +%YAML 1.2
> > > > +---
> > > > +$id: http://devicetree.org/schemas/gpio/starfive,jh7100-gpio.yaml#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +
> > > > +title: StarFive JH7100 GPIO controller
> > > > +
> > > > +maintainers:
> > > > +  - Huan Feng <huan.feng at starfivetech.com>
> > > > +  - Drew Fustini <drew at beagleboard.org>
> > > > +
> > > > +properties:
> > > > +  compatible:
> > > > +    items:
> > > > +      - const: starfive,jh7100-gpio
> > > > +
> > > > +  reg:
> > > > +    maxItems: 1
> > > > +
> > > > +  interrupts:
> > > > +    description:
> > > > +      Interrupt mapping, one per GPIO. Maximum 32 GPIOs.
> > > > +    minItems: 1
> > > > +    maxItems: 32
> > >
> > > What about clocks and resets?
> >
> > Thank you for your feedback, Geert.
> >
> > GPIO controller uses clk_apb1_bus under dom0_sys.  I believe the device
> > tree node would use something like this:
> >
> >   clocks = <&clkgen JH7100_CLK_APB1>;
> >
> > I see the sifive-gpio.yaml has:
> >
> >   clocks:
> >     maxItems: 1
> >
> > Would that be the correct way to do it for the starfive gpio yaml?
> 
> Yep.
> 
> > The reset for GPIO controller is presetn under dom_sys.  Do you think
> > know you know an example that has reset in the YAML?  Is there some code
> > that would actually make use of that information?
> >
> > >
> > > > +
> > > > +  gpio-controller: true
> > > > +
> > > > +  "#gpio-cells":
> > > > +    const: 2
> > > > +
> > > > +  interrupt-controller: true
> > > > +
> > > > +  "#interrupt-cells":
> > > > +    const: 2
> > > > +
> > > > +required:
> > > > +  - compatible
> > > > +  - reg
> > > > +  - interrupts
> > > > +  - interrupt-controller
> > > > +  - "#interrupt-cells"
> > > > +  - "#gpio-cells"
> > > > +  - gpio-controller
> >
> > Do you think I should add 'clocks' to 'required:'?
> 
> I'm still having issues with i2c if the GPIO block lists a clock, due to
> fw_devlink dependencies.
> 
> > > > +
> > > > +additionalProperties: false
> > > > +
> > > > +examples:
> > > > +  - |
> > > > +      gpio at 11910000 {
> > > > +        compatible = "starfive,jh7100-gpio";
> > > > +        reg = <0x11910000 0x10000>;
> > > > +        gpio-controller;
> > > > +        #gpio-cells = <2>;
> > > > +        interrupt-controller;
> > > > +        #interrupt-cells = <2>;
> > > > +        interrupts = <32>;
> >
> > I would add:
> >
> >   clocks = <&clkgen JH7100_CLK_APB1>;
> >
> > But I am not sure how reset would work?
> 
> That should become "resets = <&rstgen JH7100_RSTN_GPIO_APB>",
> but we don't have the reset controller in Linux yet (we do in barebox).

Do you think I should add reset item like this?

  resets:
    maxItems: 1

I suppose this is supposed to describe the hardware and it shouldn't
matter whether or not Linux uses the property, right?

Thank you,
Drew