Re: [PATCH 1/2] spi: renesas,rzv2m-csi: Add SPI Slave related properties

[Mark Brown]

On Wed, Sep 27, 2023 at 11:10:58AM +0200, Geert Uytterhoeven wrote:
> On Wed, Sep 27, 2023 at 11:00 AM Mark Brown <broonie@xxxxxxxxxx> wrote:

> > The description is clearly saying there is a chip select, _NO_CS seems
> > entirely inappropriate.  It's not specified in the device tree because
> > when there's no chip select for a device it's a fundamental property of
> > how the device is controlled and we don't need any information beyond
> > the compatible.

> In host mode, it indeed doesn't matter, as you can have only a single
> device connected with SPI_NO_CS.
> In device mode, the device needs to know if it must monitor the chip
> select line or not.

> In hindsight, I should have kept the question I had written initially,
> but deleted after having read the documentation for the corresponding
> RZ/V2M register bits:

>     What does it mean if this is false? That there is no chip select?

> So "spi-no-cs" would be the inverse of "renesas,csi-ss".

I see.  Is there any control over what the chip select is when there is
one, in which case we could just look to see if there's one specified?

I'm a bit nervous about a generic property that maps onto _NO_CS since
it's likely that people will start using that in device bindings when
they shouldn't.

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