On Fri, May 10, 2024 at 07:44:24PM -0500, David Lechner wrote: > This adds a new property to the spi-peripheral-props binding for use > with peripherals connected to controllers that support offloading. > > Here, offloading means that the controller has the ability to perform > complex SPI transactions without CPU intervention in some shape or form. > > This property will be used to assign controller offload resources to > each peripheral that needs them. What these resources are will be > defined by each specific controller binding. > > Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx> > --- > > v2 changes: > > In v1, instead of generic SPI bindings, there were only controller- > specific bindings, so this is a new patch. > > In the previous version I also had an offloads object node that described > what the offload capabilities were but it was suggested that this was > not necessary/overcomplicated. So I've gone to the other extreme and > made it perhaps over-simplified now by requiring all information about > how each offload is used to be encoded in a single u32. The property is a u32-array, so I guess, not a single u32? > We could of course consider using #spi-offload-cells instead for > allowing encoding multiple parameters for each offload instance if that > would be preferable. A -cells property was my gut reaction to what you'd written here and seems especially appropriate if there's any likelihood of some future device using some external resources for spi-offloading. However, -cells properties go in providers, not consumers, so it wouldn't end up in spi-periph-props.yaml, but rather in the controller binding, and instead there'd be a cell array type property in here. I think you know that though and I'm interpreting what's been written rather than what you meant. > I also considered adding spi-offload-names that could be used as sort > of a compatible string (more of an interface name really) in case some > peripherals may want to support more than 1 specialized type of offload. > --- > .../devicetree/bindings/spi/spi-peripheral-props.yaml | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml b/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml > index 15938f81fdce..32991a2d2264 100644 > --- a/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml > +++ b/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml > @@ -113,6 +113,16 @@ properties: > minItems: 2 > maxItems: 4 > > + spi-offloads: > + $ref: /schemas/types.yaml#/definitions/uint32-array > + description: > + Array of controller offload instances that are reserved for use by the > + peripheral device. The semantic meaning of the values of the array > + elements is defined by the controller. For example, it could be a simple > + 0-based index of the offload instance, or it could be a bitfield where > + a few bits represent the assigned hardware trigger, a few bits represent > + the assigned RX stream, etc. > + > st,spi-midi-ns: > description: | > Only for STM32H7, (Master Inter-Data Idleness) minimum time > > -- > 2.43.2 >
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