linux-kernel - Re: [PATCH 2/3] pinctrl: Device tree bindings for Qualcomm pm8xxx gpio block

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Date:	Tue, 15 Jul 2014 17:23:51 -0700
From:	Bjorn Andersson <bjorn@...o.se>
To:	"Ivan T. Ivanov" <iivanov@...sol.com>
Cc:	Stephen Boyd <sboyd@...eaurora.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bjorn Andersson <bjorn.andersson@...ymobile.com>,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/3] pinctrl: Device tree bindings for Qualcomm pm8xxx
 gpio block

On Mon, Jul 14, 2014 at 11:35 PM, Ivan T. Ivanov <iivanov@...sol.com> wrote:
> On Mon, 2014-07-14 at 14:20 -0700, Stephen Boyd wrote:
[..]
>> Isn't this document only for the gpios? I think you're talking about the
>> MPPs, which also exist on these generation of pmics. We should probably
>> avoid mixing the two (gpios and mpps) in one binding because they're
>> really different hardware.
>
> I don't know. For me "gpio" looks like function of the pin hardware.
>
>>
>> >  So I will like
>> > to keep "function" property for selecting one of the above functions.
>> > Choosing between "normal", "paired"... options in QPNP pinctrl driver
>> > is supported trough passing values, defined in DT header file, to
>> > "output-high" property. Please don't kill me :-).
>>
>> Overloading output-high to choose the MPP mode doesn't seem to follow
>> the generic pinconfig binding. Does output-high even take a value? Why
>> can't we use the function property?
>
> No, no.  using value of the output-high|low" is just to select
> "normal", "paired"... thing. Function selection is via "function"
> property. Currently QPNP support following functions "gpio", "mpp-ain",
> "mpp-aout", "mpp-cs".
>

Hi Ivan,

>From your comment I presume that you don't have access to the
documentation for these blocks.

The pmic sports two types of pins; gpios and mpps (multi-purpose-pin).
These are different hardware blocks; i.e. not a configuration thing.

The gpios can be input, output or both and they can be configured as
gpio, paired, function 1 or function 2 (+ some test modes). So here it
makes sense to have the functions "gpio", "paired" and the valid
function combinations.

The mpps can be input, output or both; in either digital or analog
mode. Or they can be a current sink. When configured as analog input
you select which adc the pin should be routed to. Here it makes sense
to have the functions "digital", "analog" and "current-sink" I think.

Regards,
Bjorn
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