On 10/26/24 10:18 AM, Jonathan Cameron wrote: > On Wed, 23 Oct 2024 15:59:12 -0500 > David Lechner <dlechner@xxxxxxxxxxxx> wrote: > >> Add a new binding for using a PWM signal as a trigger for SPI offloads. > > I don't have a better suggestion for this, but it does smell rather like > other bridge binding (iio-hwmon for example) where we have had push back on > representing something that doesn't really exist but is just a way to > tie two bits of hardware together. Those kind of exist because we snuck > them in a long time back when no one was paying attention. > > So this one may need more explanation and justification and I'd definitely > like some DT maintainer review on this at a fairly early stage! > (might have happened in earlier reviews but it has been a while so I've > forgotten if it did) > > Jonathan > We could probably make it work like the leds version of this binding where the trigger-sources property can have phandles to anything, not just a dedicated class of device. It just gets messy to implement because every subsystem needs to have core code modified to be able to handle using a device or one channel/gpio/etc. of a device as a trigger instead of whatever it normally is. > >> >> Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx> >> --- >> >> v4 changes: new patch in v4 >> --- >> .../devicetree/bindings/spi/trigger-pwm.yaml | 39 ++++++++++++++++++++++ >> 1 file changed, 39 insertions(+) >> >> diff --git a/Documentation/devicetree/bindings/spi/trigger-pwm.yaml b/Documentation/devicetree/bindings/spi/trigger-pwm.yaml >> new file mode 100644 >> index 000000000000..987638aa4732 >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/spi/trigger-pwm.yaml >> @@ -0,0 +1,39 @@ >> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) >> +%YAML 1.2 >> +--- >> +$id: http://devicetree.org/schemas/spi/trigger-pwm.yaml# >> +$schema: http://devicetree.org/meta-schemas/core.yaml# >> + >> +title: Generic SPI offload trigger using PWM >> + >> +description: Remaps a PWM channel as a trigger source. >> + >> +maintainers: >> + - David Lechner <dlechner@xxxxxxxxxxxx> >> + >> +$ref: /schemas/spi/trigger-source.yaml# >> + >> +properties: >> + compatible: >> + const: trigger-pwm >> + >> + '#trigger-source-cells': >> + const: 0 >> + >> + pwms: >> + maxItems: 1 >> + >> +required: >> + - compatible >> + - '#trigger-source-cells' >> + - pwms >> + >> +additionalProperties: false >> + >> +examples: >> + - | >> + trigger { >> + compatible = "trigger-pwm"; >> + #trigger-source-cells = <0>; >> + pwms = <&pwm 0 1000000 0>; >> + }; >> >
