linux-kernel - Re: [PATCH] spi: pxa2xx: Only claim CS GPIOs when the slave device is created

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Date:   Mon, 24 Jul 2017 12:53:20 +0200
From:   Jan Kiszka <jan.kiszka@....de>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Daniel Mack <daniel@...que.org>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        Mark Brown <broonie@...nel.org>,
        linux-spi <linux-spi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] spi: pxa2xx: Only claim CS GPIOs when the slave device is
 created

On 2017-07-24 12:44, Andy Shevchenko wrote:
> +Cc: Mika
> 
> On Sat, Jul 8, 2017 at 11:41 AM, Jan Kiszka <jan.kiszka@....de> wrote:
>> From: Jan Kiszka <jan.kiszka@...mens.com>
>>
>> Avoid hogging chip select GPIOs just because they are listed for the
>> master. They might be mulitplexed and, if no slave device is attached,
>> used for different purposes. Moreover, this strategy avoids having to
>> allocate a cs_gpiods structure.
>>
>> Tested on the IOT2000 where the second SPI bus is connected to an
>> Arduino-compatible connector and multiplexed between SPI, GPIO and PWM
>> usage.
>>
> 
> This breaks all systems which are using _DSD.

Err, can you elaborate? Worked fine here with _DSD on the IOT2000.

> 
> While I'm looking for fix, I get feeling that the approach itself is not right,
> 
> So, for now I would vote for immediate revert and then rethink what we
> can do here.

I'm fine with reverting because the patch wasn't clean anyway (mixed old
and new GPIO API) - aside from whatever you found in addition. I had an
update pending but, as you are looking into this anyway, I'm sure your
patches will be more holistic.

Thanks,
Jan



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