Re: [PATCH v3 1/2] dt-bindings: pwm: Add Xilinx AXI Timer

[Sean Anderson]

On 5/13/21 10:33 AM, Sean Anderson wrote:
>
>
> On 5/12/21 10:16 PM, Rob Herring wrote:
>  > On Tue, May 11, 2021 at 03:12:37PM -0400, Sean Anderson wrote:
>  >> This adds a binding for the Xilinx LogiCORE IP AXI Timer. This device is
>  >> a "soft" block, so it has many parameters which would not be
>  >> configurable in most hardware. This binding is usually automatically
>  >> generated by Xilinx's tools, so the names and values of some properties
>  >> must be kept as they are. Replacement properties have been provided for
>  >> new device trees.
>  >
>  > Because you have some tool generating properties is not a reason we have
>  > to accept them upstream.
>
> These properties are already in arch/microblaze/boot/dts/system.dts and
> in the devicetree supplied to Linux by qemu. Removing these properties
> will break existing setups, which I would like to avoid.
>
>  > 'deprecated' is for what *we* have deprecated.
>
> Ok. I will remove that then.
>
>  >
>  > In this case, I don't really see the point in defining new properties
>  > just to have bool.
>
> I don't either, but it was requested, by Michal...

Err, your comment on the original bindings was

> Can't all these be boolean?

And Michal commented

> I think in this case you should described what it is used by current
> driver in Microblaze and these options are required. The rest are by
> design optional.
> If you want to change them to different value then current binding
> should be deprecated and have any transition time with code alignment.

So that is what I tried to accomplish with this revision. I also tried
allowing something like

	xlnx,one-timer-only = <0>; /* two timers */
	xlnx,one-timer-only = <1>; /* one timer  */
	xlnx,one-timer-only; /* one timer */
	/* property absent means two timers */

but I was unable to figure out how to express this with json-schema. I
don't think it's the best design either...

--Sean

>
>  >
>  >>
>  >> Because we need to init timer devices so early in boot, the easiest way
>  >> to configure things is to use a device tree property. For the moment
>  >> this is 'xlnx,pwm', but this could be extended/renamed/etc. in the
>  >> future if these is a need for a generic property.
>  >
>  > No...
>  >
>  >> Signed-off-by: Sean Anderson <sean.anderson@xxxxxxxx>
>  >> ---
>  >> How should the clocking situation be documented? For the moment I have
>  >> just left clock as optional, but should clock-frequency be documented?
>  >>
>  >> Changes in v3:
>  >> - Mark all boolean-as-int properties as deprecated
>  >> - Add xlnx,pwm and xlnx,gen?-active-low properties.
>  >> - Make newer replacement properties mutually-exclusive with what they
>  >>    replace
>  >> - Add an example with non-deprecated properties only.
>  >>
>  >> Changes in v2:
>  >> - Use 32-bit addresses for example binding
>  >>
>  >>   .../bindings/pwm/xlnx,axi-timer.yaml          | 142 ++++++++++++++++++
>  >>   1 file changed, 142 insertions(+)
>  >>   create mode 100644 Documentation/devicetree/bindings/pwm/xlnx,axi-timer.yaml
>  >>
>  >> diff --git a/Documentation/devicetree/bindings/pwm/xlnx,axi-timer.yaml b/Documentation/devicetree/bindings/pwm/xlnx,axi-timer.yaml
>  >> new file mode 100644
>  >> index 000000000000..a5e90658e31a
>  >> --- /dev/null
>  >> +++ b/Documentation/devicetree/bindings/pwm/xlnx,axi-timer.yaml
>  >> @@ -0,0 +1,142 @@
>  >> +# SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
>  >> +%YAML 1.2
>  >> +---
>  >> +$id: http://devicetree.org/schemas/pwm/xlnx,axi-timer.yaml#
>  >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>  >> +
>  >> +title: Xilinx LogiCORE IP AXI Timer Device Tree Binding
>  >> +
>  >> +maintainers:
>  >> +  - Sean Anderson <sean.anderson@xxxxxxxx>
>  >> +
>  >> +properties:
>  >> +  compatible:
>  >> +    oneOf:
>  >> +      - items:
>  >> +        - const: xlnx,axi-timer-2.0
>  >> +        - const: xlnx,xps-timer-1.00.a
>  >> +      - const: xlnx,xps-timer-1.00.a
>  >> +
>  >> +  clocks:
>  >> +    maxItems: 1
>  >> +
>  >> +  clock-names:
>  >> +    const: s_axi_aclk
>  >> +
>  >> +  reg:
>  >> +    maxItems: 1
>  >> +
>  >> +  xlnx,count-width:
>  >> +    $ref: /schemas/types.yaml#/definitions/uint32
>  >> +    minimum: 8
>  >> +    maximum: 32
>  >> +    description:
>  >> +      The width of the counter(s), in bits.
>  >> +
>  >> +  xlnx,gen0-assert:
>  >> +    $ref: /schemas/types.yaml#/definitions/uint32
>  >> +    enum: [ 0, 1 ]
>  >> +    default: 1
>  >> +    deprecated: true
>  >> +    description:
>  >> +      The polarity of the generateout0 signal. 0 for active-low, 1 for active-high.
>  >> +
>  >> +  xlnx,gen0-active-low:
>  >> +    $ref: /schemas/types.yaml#/definitions/flag
>  >> +    description:
>  >> +      The generate0 signal is active-low.
>  >> +
>  >> +  xlnx,gen1-assert:
>  >> +    $ref: /schemas/types.yaml#/definitions/uint32
>  >> +    enum: [ 0, 1 ]
>  >> +    default: 1
>  >> +    deprecated: true
>  >> +    description:
>  >> +      The polarity of the generateout1 signal. 0 for active-low, 1 for active-high.
>  >> +
>  >> +  xlnx,gen1-active-low:
>  >> +    $ref: /schemas/types.yaml#/definitions/flag
>  >> +    description:
>  >> +      The generate1 signal is active-low.
>  >> +
>  >> +  xlnx,one-timer-only:
>  >> +    $ref: /schemas/types.yaml#/definitions/uint32
>  >> +    enum: [ 0, 1 ]
>  >> +    deprecated: true
>  >> +    description:
>  >> +      Whether only one timer is present in this block.
>  >> +
>  >> +  xlnx,single-timer:
>  >> +    $ref: /schemas/types.yaml#/definitions/flag
>  >> +    description:
>  >> +      Only one timer is present in this block.
>  >> +
>  >> +  xlnx,pwm:
>  >> +    $ref: /schemas/types.yaml#/definitions/flag
>  >> +    description:
>  >> +      This timer should be configured as a PWM.
>  >
>  > If a PWM, perhaps you want a '#pwm-cells' property which can serve as
>  > the hint to configure as a PWM.
>
> Ok, that's a good idea.
>
> --Sean
>
>  >
>  >> +
>  >> +required:
>  >> +  - compatible
>  >> +  - reg
>  >> +  - xlnx,count-width
>  >> +
>  >> +allOf:
>  >> +  - if:
>  >> +      required:
>  >> +        - clocks
>  >> +    then:
>  >> +      required:
>  >> +        - clock-names
>  >> +
>  >> +  - if:
>  >> +      required:
>  >> +        - xlnx,gen0-active-low
>  >> +    then:
>  >> +      not:
>  >> +        required:
>  >> +          - xlnx,gen0-assert
>  >> +
>  >> +  - if:
>  >> +      required:
>  >> +        - xlnx,gen0-active-low
>  >> +    then:
>  >> +      not:
>  >> +        required:
>  >> +          - xlnx,gen0-assert
>  >> +
>  >> +  - if:
>  >> +      required:
>  >> +        - xlnx,one-timer-only
>  >> +    then:
>  >> +      not:
>  >> +        required:
>  >> +          - xlnx,single-timer
>  >> +
>  >> +additionalProperties: true
>  >> +
>  >> +examples:
>  >> +  - |
>  >> +    axi_timer_0: timer@800e0000 {
>  >> +        clock-names = "s_axi_aclk";
>  >> +        clocks = <&zynqmp_clk 71>;
>  >> +        compatible = "xlnx,axi-timer-2.0", "xlnx,xps-timer-1.00.a";
>  >> +        reg = <0x800e0000 0x10000>;
>  >> +        xlnx,count-width = <0x20>;
>  >> +        xlnx,gen0-assert = <0x1>;
>  >> +        xlnx,gen1-assert = <0x1>;
>  >> +        xlnx,one-timer-only = <0x0>;
>  >> +        xlnx,trig0-assert = <0x1>;
>  >> +        xlnx,trig1-assert = <0x1>;
>  >> +    };
>  >> +
>  >> +  - |
>  >> +    axi_timer_0: timer@800e0000 {
>  >> +        clock-names = "s_axi_aclk";
>  >> +        clocks = <&zynqmp_clk 71>;
>  >> +        compatible = "xlnx,axi-timer-2.0", "xlnx,xps-timer-1.00.a";
>  >> +        reg = <0x800e0000 0x10000>;
>  >> +        xlnx,count-width = <0x20>;
>  >> +        xlnx,gen0-active-low;
>  >> +        xlnx,single-timer;
>  >> +    };
>  >> --
>  >> 2.25.1
>  >>