Re: [PATCH 6/7] dt-bindings: spi: stm32: add stm32h7 st,spi-slave-underrun property

[Valentin CARON]

On 4/28/23 23:56, Rob Herring wrote:
> On Fri, Apr 28, 2023 at 02:15:23PM +0200, Valentin Caron wrote:
> > This property is used to enable and configure stm32h7 SPI controller to
> > handle underrun that could appear in slave mode.
> >
> > Signed-off-by: Valentin Caron <valentin.caron@xxxxxxxxxxx>
> > ---
> >   .../devicetree/bindings/spi/st,stm32-spi.yaml     |  8 ++++++++
> >   MAINTAINERS                                       |  1 +
> >   include/dt-bindings/spi/spi-stm32.h               | 15 +++++++++++++++
> >   3 files changed, 24 insertions(+)
> >   create mode 100644 include/dt-bindings/spi/spi-stm32.h
> >
> > diff --git a/Documentation/devicetree/bindings/spi/st,stm32-spi.yaml b/Documentation/devicetree/bindings/spi/st,stm32-spi.yaml
> > index 1d26fa2658c5..e946ea71a247 100644
> > --- a/Documentation/devicetree/bindings/spi/st,stm32-spi.yaml
> > +++ b/Documentation/devicetree/bindings/spi/st,stm32-spi.yaml
> > @@ -28,6 +28,7 @@ allOf:
> >         properties:
> >           st,spi-midi-ns: false
> >           spi-slave: false
> > +        st,spi-slave-underrun: false
> >   
> >   properties:
> >     "#address-cells": true
> > @@ -70,6 +71,13 @@ properties:
> >         In case of spi-slave defined, if <0>, indicate that SS should be
> >         detected via the dedicated HW pin
> >   
> > +  st,spi-slave-underrun:
> > +    $ref: /schemas/types.yaml#/definitions/uint32-array
> > +    description:
> > +      First parameter enables and selects slave underrun reaction.
> > +      Refer to "dt-bindings/spi/spi-stm32.h" for the supported values.
> > +      Second parameter is the pattern in case of SPI_SEND_PATTERN mode.
> So, max 2 cells? Then:
>
> minItems: 1
> maxItems: 2
>
> Though I don't really think this belongs in DT. The driver implementing
> the SPI slave function defines all the rest of the protocol the slave
> implements. Why not this little bit? Perhaps there is no way for a SPI
> slave driver to tell the SPI controller which controller specific mode
> to use, so you abuse DT to configure the SPI controller. Also, with a
> controller specific response, then the slave driver is coupled to that
> SPI controller which isn't great either.
>
> Rob
I basically made this DT property to configure the controler and doesn't
give attention to the fact that this parameter can came from framework.

I will not rework this functionality, but simply let it down as we has
no demands on it.

Thanks for all your remarks,
Valentin