linux-kernel - Re: [PATCH v3 3/6] dt-bindings: mfd: da9062: add regulator voltage selection documentation

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Message-ID: <20191210094144.mxximpuouchy3fqu@pengutronix.de>
Date:   Tue, 10 Dec 2019 10:41:44 +0100
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     Mark Brown <broonie@...nel.org>
Cc:     support.opensource@...semi.com, lee.jones@...aro.org,
        robh+dt@...nel.org, linus.walleij@...aro.org,
        bgolaszewski@...libre.com, joel@....id.au, andrew@...id.au,
        lgirdwood@...il.com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-aspeed@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org, kernel@...gutronix.de
Subject: Re: [PATCH v3 3/6] dt-bindings: mfd: da9062: add regulator voltage
 selection documentation

Hi Mark,

On 19-12-04 13:46, Mark Brown wrote:
> On Fri, Nov 29, 2019 at 06:25:34PM +0100, Marco Felsch wrote:
> 
> > +  Optional regulator device-specific properties:
> > +  - dlg,vsel-sense-gpios : A GPIO reference to a local general purpose input,
> > +    the datasheet calls it GPI. The regulator sense the input signal and select
> > +    the active or suspend voltage settings. If the signal is active the
> > +    active-settings are applied else the suspend-settings are applied.
> > +    Attention: Sharing the same GPI for other purposes or across multiple
> > +    regulators is possible but the polarity setting must equal.
> 
> I'm really confused by this.  As far as I understand it it seems
> to be doing pinmuxing on the chip using the GPIO bindings which
> is itself a bit odd and I don't see anything here that configures
> whatever sets the state of the pins.  Don't we need another GPIO
> to set the vsel-sense inputs on the PMIC?

Yes the PMIC is very configurable and it took a while till I understand
it.. @Adam please correct me if I'm wrong.

The PMIC regulators regardless of the type: ldo or buck can be
simplified drawn as:



da9062-gpio               da9062-regulator
    
  +-------------------------------------------------------
  |                  PMIC
  |    
  > GPIO0            +--------------------------+
  |                  |         REGULATOR-0      |
  > GPIO1 -------+   |                          |
  |              +-- > vsel-in    voltage-a-out <
  > GPIO2        |   |                          |
  |              |   > enable-in  voltage-b-out <
  |              |   |                          |
  |              |   +--------------------------+
  |              |                              
  |              |   +--------------------------+                          
  |              |   |         REGULATOR-1      |                          
  |              |   |                          |                          
  |              +-- > vsel-in    voltage-a-out <                          
  |                  |                          |                          
  |                  > enable-in  voltage-b-out <
  |                  |                          |
  |                  +--------------------------+
  |

The 'vsel-in' and 'enable-in' regulator inputs must be routed to the
PMIC GPIOs which must be configured as input. If this is a pinmux in
your opinion, then yes we need to do that. IMHO it isn't a pinmux
because from the regulator point of view it is just a GPIO which comes
from our own gpio-dev (da9062-gpio). So the abstraction is vald. Anyway
I'm with you that this isn't the typical use-case.

Regards,
  Marco 

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