linux-kernel - Re: [PATCH] ARM: at91: spi: request all csgpio in spi probe

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Date:	Fri, 1 Aug 2014 01:05:24 +0800
From:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Cc:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	Boris BREZILLON <boris.brezillon@...e-electrons.com>,
	devicetree@...r.kernel.org,
	Jiří Prchal <jiri.prchal@...ignal.cz>,
	Nicolas FERRE <nicolas.ferre@...el.com>,
	linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>,
	voice.shen@...el.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: at91: spi: request all csgpio in spi probe


On Aug 1, 2014, at 12:48 AM, Alexandre Belloni <alexandre.belloni@...e-electrons.com> wrote:

> 
> On 01/08/2014 at 00:10:05 +0800, Jean-Christophe PLAGNIOL-VILLARD wrote :
>>>>> While this solves the particular issue Jiří is seeing, this will not
>>>>> solve the case where PA14 (CS0) is not used by the spi driver at all. It
>>>>> will remained muxed as CS0 and toggle when the spi master needs to
>>>>> access CS0 until another driver muxes it to something else. I still
>>>>> believe we should explicitly ask pinctrl to mux them as gpios.
>> 
>> This is not the job of the kernel but to the bootloader
>> no the pinctrl binding is not here and will never be here the configure a pin as a GPIO or
> 
> This is exactly what AT91_PERIPH_GPIO does though. Anyway, not request
> the pinmuxing in the driver is not a good idea, then nothing prevents
> another driver to request them to do something completely different.

here it’s the same issue if you need to pin as GPIO use the GPIO API not the pinctrl

AT91_PERIPH_GPIO is use the set specific pinmux (bouncing & etc…)


> 
>> to a specific state. This the job of the driver or the bootloader
>> 
> 
> I agree that it must not allow to set the state, we are talking about
> muxing.
> 
> 
> -- 
> Alexandre Belloni, Free Electrons
> Embedded Linux, Kernel and Android engineering
> http://free-electrons.com

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