linux-kernel - Re: [PATCH v4] ARM: dts: sun8i: Add dts file for Olimex A33-OLinuXino

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Date:	Wed, 27 Jul 2016 13:02:41 +0300
From:	stefan.mavrodiev@...il.com
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:	stefan.mavrodiev@...il.com, dt@...nel.org, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, linux@...linux.org.uk, wens@...e.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [PATCH v4] ARM: dts: sun8i: Add dts file for Olimex A33-OLinuXino

On Wednesday, July 27, 2016 8:21:46 AM EEST Maxime Ripard wrote:
> On Wed, Jul 27, 2016 at 08:12:29AM +0300, stefan.mavrodiev@...il.com wrote:
> > > > +&reg_dcdc1 {
> > > > +	regulator-always-on;
> > > > +	regulator-min-microvolt = <3300000>;
> > > > +	regulator-max-microvolt = <3300000>;
> > > > +	regulator-name = "vcc-dsi";
> > > > +};
> > > 
> > > What is it used for? Is it really necessary to keep it on at all time?
> > 
> > I think so.
> > This is the supply for the MMC.
> 
> Then it's poorly named, and you should tie it to the MMC, and remove
> the always-on if it's only used by the mmc. always-on is supposed to
> be for regulators that shouldn't but turned off for the system to stay
> running. Some MMC regulator doesn't fit that description.
> 
It's named upon the A33 power pin - "VCC-DSI". 
If I remove "always-on" the board still will work, since dcdc1 is tied to 
mmc0. 
vmmc-supply = <&reg_dcdc1>;

We assume this voltage will be always present and there are some pullups that 
are tied to it (on i2c0 and i2c1 bus).  In this case should I remove "always-
on" from the regulator node?

> Maxime

Best regards,
Stefan Mavrodiev