linux-kernel - Re: [PATCH 3/4] ARM: pinctrl: Add Broadcom Capri pinctrl driver

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Date:	Mon, 4 Nov 2013 13:24:10 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Sherman Yin <syin@...adcom.com>,
	Heiko Stübner <heiko@...ech.de>,
	Laxman Dewangan <ldewangan@...dia.com>
Cc:	Mark Rutland <mark.rutland@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Christian Daudt <bcm@...thebug.org>,
	Russell King <linux@....linux.org.uk>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Stephen Warren <swarren@...dotorg.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rob Herring <rob.herring@...xeda.com>,
	bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
	Rob Landley <rob@...dley.net>,
	Grant Likely <grant.likely@...aro.org>,
	Matt Porter <matt.porter@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 3/4] ARM: pinctrl: Add Broadcom Capri pinctrl driver

On Sat, Oct 26, 2013 at 12:48 AM, Sherman Yin <syin@...adcom.com> wrote:

> So I will go ahead and make the change in pinconf-generic.c and pinctrl-bindings.txt
> to include parsing of the "slew-rate" property and submit it as part of my pinctrl
> changes.

OK, good.

> Question regarding pinctrl-generic: in pinctrl-bindings.txt, this is said about the
> "function" property:
>
> 169- function takes a list of function names/IDs as a required argument. The
> 170  specific binding for the hardware defines:
> 171  - Whether the entries are integers or strings, and their meaning.
> 172  - Whether only a single entry is allowed (which is applied to all entries
> 173    in the pins property), or whether there may alternatively be one entry per
> 174    entry in the pins property, in which case the list lengths must match, and
> 175    for each list index i, the function at list index i is applied to the pin
> 176    at list index i.
>
> (Although it looks like pinconf_generic_dt_subnode_to_map() does not support
> the "one entry per pin feature" for the "function" property yet.)
>
> In my driver, I have the "one entry per pin" support for all my properties instead
> of just the function property, like the "drive_str" property below:
>
> +               grp_1 {
> +                       brcm,pins       = "pin1", "pin2", "pin3";
> +                       brcm,function   = "alt1", "alt2", "alt1";
> +                       brcm,drive_str  = <2 4 6>;
> +                       brcm,slew       = <1>;
> +               };

OK.

> I thought that would be convenient and allow users to group pins together based
> on functionality and without the restriction that the pins must have the same
> properties.  Do you think that's a good idea and are there plans to support that in
> the generic pinconfig?  If so, I can look into porting my implementation to
> pinconf-generic.c - but first I have to figure out how some of the properties would
> work if more than one value could be specified (eg. "bias-disable" which takes no
> values)

Hm I don't quite get it I think. It depends on the old bindings still working
and full compatibility with old device trees. It might be a bit confusing.

I need help from Heiko on this I think.

Yours,
Linus Walleij
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