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Message-ID: <70176596-2250-8ae1-912a-9f9c30694e7d@seco.com>
Date: Thu, 13 May 2021 11:28:36 -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 5/13/21 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@...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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