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SubjectRe: [PATCH] ARM: dts: sunxi: Add num-cs for A20 spi nodes
On Thu, 24 Nov 2016 20:55:17 +0100
Maxime Ripard <maxime.ripard@free-electrons.com> wrote:

> On Tue, Nov 22, 2016 at 06:06:16PM +0100, Emmanuel Vadot wrote:
> > The spi0 controller on the A20 have up to 4 CS (Chip Select) while the
> > others three only have 1.
> > Add the num-cs property to each node.
> >
> > Signed-off-by: Emmanuel Vadot <manu@bidouilliste.com>
>
> I don't think we have any code that uses it at the moment. What is the
> rationale behind this patch?
>
> Thanks!
> Maxime
>
> --
> Maxime Ripard, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com

Hi Maxime,

If num-cs isn't present nothing prevent to start a transfer with a
non-valid CS pin, resulting in an error.
num-cs are default property especially made for this and a SPI driver
should try to get the property at probe/attach time.

Cheers,

--
Emmanuel Vadot <manu@bidouilliste.com> <manu@freebsd.org>

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