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Date: Thu, 13 May 2021 10:33:44 -0400
From: Sean Anderson <sean.anderson@...o.com>
To: Rob Herring <robh@...nel.org>
Cc: linux-pwm@...r.kernel.org, devicetree@...r.kernel.org,
michal.simek@...inx.com, Alvaro Gamez <alvaro.gamez@...ent.com>,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/2] dt-bindings: pwm: Add Xilinx AXI Timer
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@...o.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@...o.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@...e0000 {
>> + 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@...e0000 {
>> + 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
>>
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