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Subject: Re: [PATCH v3 1/2] dt-bindings: pwm: Add Xilinx AXI Timer
To:     Rob Herring <robh@kernel.org>
Cc:     linux-pwm@vger.kernel.org, devicetree@vger.kernel.org,
        michal.simek@xilinx.com, Alvaro Gamez <alvaro.gamez@hazent.com>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
References: <20210511191239.774570-1-sean.anderson@seco.com>
 <20210513021631.GA878860@robh.at.kernel.org>
From:   Sean Anderson <sean.anderson@seco.com>
Message-ID: <f9165937-c578-d225-9f5e-d964367c4711@seco.com>
Date:   Thu, 13 May 2021 10:33:44 -0400
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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...

 >
 >>
 >> 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@seco.com>
 >> ---
 >> 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@seco.com>
 >> +
 >> +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
 >>