Re: [PATCH v14 07/16] dt-bindings: fix sifive gpio properties

[Rob Herring <robh@kernel.org>]

On Wed, Feb 3, 2021 at 6:47 PM Damien Le Moal <Damien.LeMoal@wdc.com> wrote:
>
> On Wed, 2021-02-03 at 14:41 -0600, Rob Herring wrote:
> > On Wed, Feb 3, 2021 at 6:52 AM Damien Le Moal <Damien.LeMoal@wdc.com> wrote:
> > >
> > > On Tue, 2021-02-02 at 13:02 -0600, Rob Herring wrote:
> > > > On Tue, Feb 2, 2021 at 4:36 AM Damien Le Moal <damien.lemoal@wdc.com> wrote:
> > > > >
> > > > > The sifive gpio IP block supports up to 32 GPIOs. Reflect that in the
> > > > > interrupts property description and maxItems. Also add the standard
> > > > > ngpios property to describe the number of GPIOs available on the
> > > > > implementation.
> > > > >
> > > > > Also add the "canaan,k210-gpiohs" compatible string to indicate the use
> > > > > of this gpio controller in the Canaan Kendryte K210 SoC. If this
> > > > > compatible string is used, do not define the clocks property as
> > > > > required as the K210 SoC does not have a software controllable clock
> > > > > for the Sifive gpio IP block.
> > > > >
> > > > > Cc: Paul Walmsley <paul.walmsley@sifive.com>
> > > > > Cc: Rob Herring <robh@kernel.org>
> > > > > Cc: devicetree@vger.kernel.org
> > > > > Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> > > > > ---
> > > > >  .../devicetree/bindings/gpio/sifive,gpio.yaml | 21 ++++++++++++++++---
> > > > >  1 file changed, 18 insertions(+), 3 deletions(-)
> > > > >
> > > > > diff --git a/Documentation/devicetree/bindings/gpio/sifive,gpio.yaml b/Documentation/devicetree/bindings/gpio/sifive,gpio.yaml
> > > > > index ab22056f8b44..2cef18ca737c 100644
> > > > > --- a/Documentation/devicetree/bindings/gpio/sifive,gpio.yaml
> > > > > +++ b/Documentation/devicetree/bindings/gpio/sifive,gpio.yaml
> > > > > @@ -16,6 +16,7 @@ properties:
> > > > >        - enum:
> > > > >            - sifive,fu540-c000-gpio
> > > > >            - sifive,fu740-c000-gpio
> > > > > +          - canaan,k210-gpiohs
> > > > >        - const: sifive,gpio0
> > > > >
> > > > >    reg:
> > > > > @@ -23,9 +24,9 @@ properties:
> > > > >
> > > > >    interrupts:
> > > > >      description:
> > > > > -      interrupt mapping one per GPIO. Maximum 16 GPIOs.
> > > > > +      interrupt mapping one per GPIO. Maximum 32 GPIOs.
> > > > >      minItems: 1
> > > > > -    maxItems: 16
> > > > > +    maxItems: 32
> > > > >
> > > > >    interrupt-controller: true
> > > > >
> > > > > @@ -38,6 +39,10 @@ properties:
> > > > >    "#gpio-cells":
> > > > >      const: 2
> > > > >
> > > > > +  ngpios:
> > > > > +    minimum: 1
> > > > > +    maximum: 32
> > > >
> > > > What's the default as obviously drivers already assume something.
> > > >
> > > > Does a driver actually need to know this? For example, does the
> > > > register stride change or something?
> > > >
> > > > Please don't add it if the only purpose is error check your DT (IOW,
> > > > if it just checks the max cell value in gpios phandles).
> > >
> > > If I remove that, make dtbs_check complains. Looking at othe gpio controller
> > > bindings, they all have it. So isn't it better to be consistent, and avoid make
> > > dtbs_check errors ?
> >
> > That would mean you are already using 'ngpios' and it is undocumented
> > (for this binding). If already in use and possibly having users then
> > that changes things, but that's not what the commit msg says.
> >
> > Not *all* gpio controllers have ngpios. It's a good number, but
> > probably more than need it though. If we wanted it everywhere, there
> > would be a schema enforcing that.
>
> If I remove the minimum and maximum lines, I get this error:

I never said remove minimum/maximum. The suggestion is either add
'default: 16' or remove 'ngpios' entirely.

> ./Documentation/devicetree/bindings/gpio/sifive,gpio.yaml:42:10: [error] empty
> value in block mapping (empty-values)
>   CHKDT   Documentation/devicetree/bindings/processed-schema-examples.json
> /home/damien/Projects/RISCV/linux/Documentation/devicetree/bindings/gpio/sifive
> ,gpio.yaml: properties:ngpios: None is not of type 'object', 'boolean'
>   SCHEMA  Documentation/devicetree/bindings/processed-schema-examples.json
> /home/damien/Projects/RISCV/linux/Documentation/devicetree/bindings/gpio/sifive
> ,gpio.yaml: ignoring, error in schema: properties: ngpios
> warning: no schema found in file:
> ./Documentation/devicetree/bindings/gpio/sifive,gpio.yaml

ngpios: true

or

ngpios: {}

Are the minimum valid values for a key. (Though not what should be done here.)

>
> If I remove the ngpios property entirely, then I get a hit on the device tree:
>
>   CHECK   arch/riscv/boot/dts/canaan/sipeed_maix_bit.dt.yaml
> /linux/arch/riscv/boot/dts/canaan/sipeed_maix_bit.dt.yaml:
> gpio-controller@38001000: 'ngpios' does not match any of the regexes: 'pinctrl-
> [0-9]+'
>         From schema:
> /home/damien/Projects/RISCV/linux/Documentation/devicetree/bindings/gpio/sifive
> ,gpio.yaml

That's not upstream, right? Then fix it.

> Now, If I change the property definition to this:
>
> diff --git a/Documentation/devicetree/bindings/gpio/sifive,gpio.yaml
> b/Documentation/devicetree/bindings/gpio/sifive,gpio.yaml
> index 2cef18ca737c..5c7865180383 100644
> --- a/Documentation/devicetree/bindings/gpio/sifive,gpio.yaml
> +++ b/Documentation/devicetree/bindings/gpio/sifive,gpio.yaml
> @@ -40,8 +40,11 @@ properties:
>      const: 2
>
>    ngpios:
> -    minimum: 1
> -    maximum: 32
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      The number of GPIO pins implemented by the controller.
> +      It is 16 for the SiFive SoCs and 32 for the Canaan K210 SoC.
> +
>
>    gpio-controller: true
>
> Then all is OK.
>
> Which option should I go for here ? If we want to avoid a dtbs_check error, as
> far as I can see, we can:
> 1) Remove the ngpios property and remove its use from the DTS, which is not
> nice in my opinion

Again, it depends if there are users depending on it. A user being a
GPIO driver somewhere, not a DTS file. The GPIO driver in the kernel
doesn't need it. So u-boot? BSD?

> 2) Use the modification proposed above