linux-kernel - Re: [PATCH] ARM: at91: at91sam9x5: sets NPCS0 (PA14) back to GPIO

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Date:	Thu, 24 Jul 2014 17:06:43 +0200
From:	Jiří Prchal <jiri.prchal@...ignal.cz>
To:	Boris BREZILLON <boris.brezillon@...e-electrons.com>
CC:	Bo Shen <voice.shen@...el.com>, nicolas.ferre@...el.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH] ARM: at91: at91sam9x5: sets NPCS0 (PA14) back to GPIO

Hi,

Dne 24.7.2014 v 16:26 Boris BREZILLON napsal(a):
> Hello Jiří,
>
> First of all, please try to use git format-patch when submitting a
> patch to any kernel mailing list.
Sorry for that.
>
> On Thu, 24 Jul 2014 15:38:24 +0200
> Jiří Prchal <jiri.prchal@...ignal.cz> wrote:
>
>> After ROMBOOT tries boot from flash on SPI0 NPCS0, this NPCS0 (PA14) remains set to PERIPH_A.
>> Because of that, this pin is unusable to something else.
>> This patch sets it back to GPIO.
>
> The policy is to leave pins in an unknown state till some peripheral
> need them.
>
> What are you trying to use this pin for ?
For chip select, but #3. And when SPI communicate with cs0 (PA22), it goes down too (PA14), so 2 devices on bus were 
selected.
> If you just want to use it as a chip select for an spi device, take a
> look at [1].
At [1] it's OK until as cs0 is for example PA22 and cs1 is PA14.
>
> Here the gpio is requested by the spi core when defining the cs-gpios
> property. The gpio controller then request the listed pins to the pin
> controller (pinctrl driver).
GPIO is not set in driver as GPIO, at least I didn't find it.
>
> You can explicitly define a new pinctrl state (by defining a new
> pinctrl_spi0_cs0 subnode in your dts file) and reference it in the
> spi0 node, though this is not mandatory.
>
> Best Regards,
>
> Boris
>
> [1]http://lxr.free-electrons.com/source/arch/arm/boot/dts/at91sam9x5ek.dtsi#L85
>
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