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Date:   Wed, 11 Oct 2023 11:01:23 +0000
From:   Sakari Ailus <sakari.ailus@iki.fi>
To:     Kieran Bingham <kieran.bingham@ideasonboard.com>
Cc:     linux-media@vger.kernel.org, devicetree@vger.kernel.org,
        "Paul J. Murphy" <paul.j.murphy@intel.com>,
        Daniele Alessandrelli <daniele.alessandrelli@intel.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        NXP Linux Team <linux-imx@nxp.com>, moderated list:
        ARM/FREESCALE IMX / MXC ARM ARCHITECTURE 
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Subject: Re: [PATCH 1/5] media: dt-bindings: media: imx335: Add supply
 bindings
Message-ID: <ZSaAg8aSZAfxEDpM@valkosipuli.retiisi.eu>
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Hi Kieran,

On Tue, Oct 10, 2023 at 02:25:09PM +0100, Kieran Bingham wrote:
> Hi Sakari,
> 
> Quoting Sakari Ailus (2023-10-10 07:06:26)
> > Hi Kieran,
> > 
> > On Tue, Oct 10, 2023 at 01:51:22AM +0100, Kieran Bingham wrote:
> > > Add the bindings for the supply references used on the IMX335.
> > > 
> > > Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> > > ---
> > >  .../bindings/media/i2c/sony,imx335.yaml          | 16 ++++++++++++++++
> > >  1 file changed, 16 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/media/i2c/sony,imx335.yaml b/Documentation/devicetree/bindings/media/i2c/sony,imx335.yaml
> > > index a167dcdb3a32..1863b5608a5c 100644
> > > --- a/Documentation/devicetree/bindings/media/i2c/sony,imx335.yaml
> > > +++ b/Documentation/devicetree/bindings/media/i2c/sony,imx335.yaml
> > > @@ -32,6 +32,15 @@ properties:
> > >      description: Clock frequency from 6 to 27 MHz, 37.125MHz, 74.25MHz
> > >      maxItems: 1
> > >  
> > > +  avdd-supply:
> > > +    description: Analog power supply (2.9V)
> > > +
> > > +  ovdd-supply:
> > > +    description: Interface power supply (1.8V)
> > > +
> > > +  dvdd-supply:
> > > +    description: Digital power supply (1.2V)
> > 
> > I wonder what's the policy in this case --- some of the regulators are
> > often hard-wired and the bindings didn't have them previously either (I
> > wonder why, maybe they were all hard wired in the board??).
> > 
> > Could they be optional? The driver will need to be able to do without these
> > in any case.
> 
> Indeed - many devices do not need to define how they are powered up.
> 
> But Krzysztof stated that supplies should be required by the bindings on
> my recent posting for a VCM driver:
> 
>  - https://lore.kernel.org/all/6e163f4d-061d-3c20-4c2e-44c74d529f10@linaro.org/
> 
> So based on that I have made these 'required'.

I guess it's good to align bindings regarding this, in practice the driver
will need to work without regulators (or with dummies), too.

> 
> Even in my case here, with a camera module that is compatible with the
> Raspberry Pi camera connector - there isn't really 3 supplies. It's just
> a single gpio enable pin to bring this device up for me. Of course
> that's specific to the module not the sensor.

How do you declare that in DT? One of the regulators will be a GPIO one?

-- 
Regards,

Sakari Ailus