linux-kernel - Re: [PATCH 1/2] pinctrl: add function to parse generic pinconfig properties from a dt node

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Message-Id: <201306131635.21446.heiko@sntech.de>
Date:	Thu, 13 Jun 2013 16:35:20 +0200
From:	Heiko Stübner <heiko@...ech.de>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	James Hogan <james.hogan@...tec.com>,
	Patrice Chotard <patrice.chotard.st@...il.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] pinctrl: add function to parse generic pinconfig properties from a dt node

Am Donnerstag, 13. Juni 2013, 10:11:28 schrieb Linus Walleij:
> Tisdagen den 13:e Juni 2013 klock 12:22 AM, skrev Heiko Stübner
> 
> <heiko@...ech.de>:
> > Am Mittwoch, 12. Juni 2013, 16:55:12 schrieb James Hogan:
> >> > +static struct pinconf_generic_dt_params dt_params[] = {
> >> > +   { "bias-disable", PIN_CONFIG_BIAS_DISABLE, 0 },
> >> > +   { "bias-high-impedance", PIN_CONFIG_BIAS_HIGH_IMPEDANCE, 0 },
> >> > +   { "bias-bus-hold", PIN_CONFIG_BIAS_BUS_HOLD, 0 },
> >> > +   { "bias-pull-up", PIN_CONFIG_BIAS_PULL_UP, 0 },
> >> > +   { "bias-pull-down", PIN_CONFIG_BIAS_PULL_DOWN, 0 },
> >> > +   { "bias-pull-pin-default", PIN_CONFIG_BIAS_PULL_PIN_DEFAULT, 0 },
> >> > +   { "drive-push-pull", PIN_CONFIG_DRIVE_PUSH_PULL, 0 },
> >> > +   { "drive-open-drain", PIN_CONFIG_DRIVE_OPEN_DRAIN, 0 },
> >> > +   { "drive-open-source", PIN_CONFIG_DRIVE_OPEN_SOURCE, 0 },
> >> > +   { "drive-strength", PIN_CONFIG_DRIVE_STRENGTH, 0 },
> >> > +   { "input-schmitt-enable", PIN_CONFIG_INPUT_SCHMITT_ENABLE, 1 },
> >> > +   { "input-schmitt-disable", PIN_CONFIG_INPUT_SCHMITT_ENABLE, 0 },
> >> > +   { "input-schmitt", PIN_CONFIG_INPUT_SCHMITT, 0 },
> >> > +   { "input-debounce", PIN_CONFIG_INPUT_DEBOUNCE, 0 },
> >> > +   { "power-source", PIN_CONFIG_POWER_SOURCE, 0 },
> >> > +   { "slew-rate", PIN_CONFIG_SLEW_RATE, 0 },
> >> > +   { "low-power-mode", PIN_CONFIG_LOW_POWER_MODE, 0 },
> >> > +   { "output-low", PIN_CONFIG_OUTPUT, 0, },
> >> > +   { "output-high", PIN_CONFIG_OUTPUT, 1, },
> >> 
> >> shouldn't half of these default to 1 instead of 0? i.e. it's much nicer
> >> for the lone flag "bias-pull-up" to enable pull up rather than disable
> >> it (you even do this in the DT example in the bindings doc).
> > 
> > on closer inspection it seems that you may be right.
> 
> Heiko can you write a patch for this? You can hit both this code and
> the Rockchip driver at the same time for sure. Please check that
> the bindings are consistent.
> 
> > The documentation to the
> > options in the pinconf-generic header even tells that for example the
> > pull options do have a 0 or 1 argument.
> 
> Yeah. Well.
> 
> Actually there has been plans to have the argument represent the
> number of Ohms on the pull-up, but we haven't seen any hardware
> that can actually select that.
> 
> Maybe we should add that now? It will still be that != 0 implies
> enablement on platforms that does not support specifying the
> pull up/down resistance.

Ok, I'll see that I get this fixed :-)


> 
> > But I'm not sure if I understand everything correctly :-) ... isn't the
> > bias- disable the opposite of turning on a pull (like the sh-pfc/pinctrl
> > does) and same with switching from one pull type to another, i.e.
> > activating a pull up would turn off a pull down and on the whole making
> > the argument redundant?
> 
> This is true, and the plan is surely for the core to not allow or print
> a big fat warning if someone does something really stupid like
> activate pull up and pull down at the same time (unless s/he's
> constructing a heater radiator or something).
> 
> Currently we don't make any sanity checks like that, BUT your
> generic parser could actually be extended to do that.
> 
> Patches welcome ;-)

I don't seem to get of the hook here ;-)

But I'll try to fix the issue above first.


> > The only other candidate I could find was low-power-mode which really
> > could use a "1" as default. All the other pinconf options either use
> > custom arguments or ignore teir argument.
> 
> A "1" for what? Not quite following....

According to the pinconf header docs, low-power-mode also expects an argument 
of 1 or 0. So it's default value should change too ... or we could rename the 
property, like "low-power-enable" and "low-power-disable", which might make 
the dt more readable than an arbitary low-power-mode = <0>;


Heiko
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