linux-kernel - Re: [PATCH 1/2] pinctrl: palmas: do not abort pin configuration for BIAS

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Date:	Wed, 2 Oct 2013 13:20:51 +0200
From:	Heiko Stübner <heiko@...ech.de>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Stephen Warren <swarren@...dotorg.org>,
	Laxman Dewangan <ldewangan@...dia.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] pinctrl: palmas: do not abort pin configuration for BIAS_DEFAULT

Am Mittwoch, 2. Oktober 2013, 12:40:14 schrieb Linus Walleij:
> On Fri, Sep 27, 2013 at 6:06 PM, Stephen Warren <swarren@...dotorg.org> 
wrote:
> > [Laxman]
> > 
> >> Hmm.. When I added the PIN_DEFAULT, I just though that do not update
> >> anything in the register and implemented like that.
> >> There is nothing "default" option in HW.
> > 
> > The description of that pinconfig option is:
> >> 7970cb77 (Heiko Stübner    2013-06-06 16:44:25 +0200  43)  *
> >> @PIN_CONFIG_BIAS_PULL_PIN_DEFAULT: the pin will be pulled up or down
> >> based 70637a6d (Heiko Stübner    2013-06-25 14:55:42 +0200  44)  *   
> >> on embedded knowledge of the controller hardware, like current mux
> >> 70637a6d (Heiko Stübner    2013-06-25 14:55:42 +0200  45)  *   
> >> function. The pull direction and possibly strength too will normally
> >> 70637a6d (Heiko Stübner    2013-06-25 14:55:42 +0200  46)  *    be
> >> decided completely inside the hardware block and not be readable
> >> 70637a6d (Heiko Stübner    2013-06-25 14:55:42 +0200  47)  *    from
> >> the kernel side. 5ca3353b (Linus Walleij    2013-06-16 12:43:06 +0200 
> >> 48)  *    If the argument is != 0 pull up/down is enabled, if it is 0,
> >> the 5ca3353b (Linus Walleij    2013-06-16 12:43:06 +0200  49)  *   
> >> configuration is ignored. The proper way to disable it is to use
> >> 5ca3353b (Linus Walleij    2013-06-16 12:43:06 +0200  50)  *   
> >> @PIN_CONFIG_BIAS_DISABLE.
> > 
> > If the HW doesn't support any concept of a default pull, I think the
> > driver shouldn't support that option; it should return an error if asked
> > to program it.
> 
> Yes that's how I remember it and how we specified it.
> Correct Heiko?

Correct. The option was/is meant for hardware that sets pull settings without 
telling the kernel specifics and the kernel also not being able to influence 
them.


Heiko
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