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To: Linus Walleij <linus.walleij@linaro.org>
Subject: Re: [PATCH 00/13] Ingenic JZ4740 / JZ4780 pinctrl driver
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Date: Fri, 20 Jan 2017 11:17:28 +0100
From: Paul Cercueil <paul@crapouillou.net>
Cc: Thierry Reding <thierry.reding@gmail.com>,
        Rob Herring <robh+dt@kernel.org>, Mark Rutland <mark.rutland@arm.com>,
        Ralf Baechle <ralf@linux-mips.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Boris Brezillon <boris.brezillon@free-electrons.com>,
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        Maarten ter Huurne <maarten@treewalker.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Paul Burton <paul.burton@imgtec.com>, linux-gpio@vger.kernel.org,
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        Linux MIPS <linux-mips@linux-mips.org>, linux-mmc@vger.kernel.org,
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        linux-fbdev@vger.kernel.org, James Hogan <james.hogan@imgtec.com>
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Le 2017-01-20 09:40, Linus Walleij a écrit :

> On Thu, Jan 19, 2017 at 12:19 PM, Paul Cercueil <paul@crapouillou.net> 
> wrote:
> 
>> The problem with pinctrl and PWM, is that the pinctrl API works by 
>> "states". A default state, sleep state, and basically any custom state 
>> that the devicetree provides. This works well until you need to 
>> control individually each pin; with 8 pins, you would need 2^8 states, 
>> each one corresponding to a given configuration.
> 
> I do not really understand, do you really use all 2^8 states in a given
> system?
> 
> The pin control states are to be used for practical situations, not
> for all theoretical situations.
> 
> You should define in your device tree the states that your
> particular system will use. Not all possible states on all possible
> systems.
> 

Well, that was if I wanted to dynamically set/unset the pin mux and
configuration when requesting/freeing a PWM. Then I'd need 2^x states
for X PWM pins.

Anyway, a static configuration works for me too. If at some point I
want dynamic configuration of the pins then I'll make the PWM driver
handle only one PWM pin and create one driver instance for each pin.

Regards,
-Paul