Messages in this thread | | | Date | Thu, 24 Nov 2016 21:05:09 +0100 | From | Emmanuel Vadot <> | Subject | Re: [PATCH] ARM: dts: sunxi: Add num-cs for A20 spi nodes |
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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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