[RFC PATCH] spi: Ensure that CS line is in non-active state after setup

[RFC PATCH] spi: Ensure that CS line is in non-active state after setup

[Ivan T. Ivanov]

When drivers didn't provide setup() method, SPI core should ensure
that CS line is driven in non-active state after spi_setup().

Signed-off-by: Ivan T. Ivanov <iivanov@mm-sol.com>
---
 drivers/spi/spi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index c64a3e5..bfba2d9 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1895,6 +1895,8 @@ int spi_setup(struct spi_device *spi)

 	if (spi->master->setup)
 		status = spi->master->setup(spi);
+	else
+		spi_set_cs(spi, false);

 	dev_dbg(&spi->dev, "setup mode %d, %s%s%s%s%u bits/w, %u Hz max --> %d\n",
 			(int) (spi->mode & (SPI_CPOL | SPI_CPHA)),
--
1.9.1

Re: [RFC PATCH] spi: Ensure that CS line is in non-active state after setup

[Mark Brown]

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On Fri, Mar 06, 2015 at 05:45:15PM +0200, Ivan T. Ivanov wrote:

>  	if (spi->master->setup)
>  		status = spi->master->setup(spi);
> +	else
> +		spi_set_cs(spi, false);

Why would this be conditional on there not being a setup operation?
It's a good idea, I just don't see why the backstop isn't always useful.

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Re: [RFC PATCH] spi: Ensure that CS line is in non-active state after setup

[Ivan T. Ivanov]

On Sun, 2015-03-08 at 20:01 +0000, Mark Brown wrote:
> On Fri, Mar 06, 2015 at 05:45:15PM +0200, Ivan T. Ivanov wrote:
> 
> >         if (spi->master->setup)
> >                 status = spi->master->setup(spi);
> > +       else
> > +               spi_set_cs(spi, false);
> 
> Why would this be conditional on there not being a setup operation?
> It's a good idea, I just don't see why the backstop isn't always useful.

I was thinking that this is expected to be handled inside
setup operation, nothing more.

Ivan 

Re: [RFC PATCH] spi: Ensure that CS line is in non-active state after setup

[Andy Shevchenko]

On Mon, Mar 9, 2015 at 9:11 AM, Ivan T. Ivanov <iivanov@mm-sol.com> wrote:
>
> On Sun, 2015-03-08 at 20:01 +0000, Mark Brown wrote:
>> On Fri, Mar 06, 2015 at 05:45:15PM +0200, Ivan T. Ivanov wrote:
>>
>> >         if (spi->master->setup)
>> >                 status = spi->master->setup(spi);
>> > +       else
>> > +               spi_set_cs(spi, false);
>>
>> Why would this be conditional on there not being a setup operation?
>> It's a good idea, I just don't see why the backstop isn't always useful.
>
> I was thinking that this is expected to be handled inside
> setup operation, nothing more.

Agree with Mark. It's perhaps a good idea to call unconditionally
before ->setup().


-- 
With Best Regards,
Andy Shevchenko