linux-kernel - Re: [RFC 5/5] arm64: dts: imx8mq: Add the opp table and the cpu-supply nodes

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Date:   Thu, 14 Feb 2019 18:32:40 +0100
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Abel Vesa <abel.vesa@....com>
Cc:     Rob Herring <robh@...nel.org>, Stephen Boyd <sboyd@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mike Turquette <mturquette@...libre.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        Angus Ainslie <angus.ainslie@...i.sm>,
        Anson Huang <anson.huang@....com>,
        dl-linux-imx <linux-imx@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [RFC 5/5] arm64: dts: imx8mq: Add the opp table and the
 cpu-supply nodes

Am Donnerstag, den 14.02.2019, 18:26 +0100 schrieb Lucas Stach:
> Am Donnerstag, den 14.02.2019, 17:18 +0000 schrieb Abel Vesa:
> > On 19-02-14 16:50:28, Lucas Stach wrote:
> > > Hi Abel
> > > 
> > > Am Mittwoch, den 13.02.2019, 19:05 +0000 schrieb Abel Vesa:
> > > > Add the opp table containing only non over drive opps.
> > > > Also add the cpu-supply nodes for the A53 cores in the EVK
> > > > board.
> > > > 
> > > > Signed-off-by: Abel Vesa <abel.vesa@....com>
> > > > ---
> > > >  arch/arm64/boot/dts/freescale/imx8mq-evk.dts | 17
> > > > +++++++++++++++++
> > > >  arch/arm64/boot/dts/freescale/imx8mq.dtsi    | 23
> > > > +++++++++++++++++++++++
> > > >  2 files changed, 40 insertions(+)
> > > > 
> > > > diff --git a/arch/arm64/boot/dts/freescale/imx8mq-evk.dts
> > > > b/arch/arm64/boot/dts/freescale/imx8mq-evk.dts
> > > > index 54737bf..114359e 100644
> > > > --- a/arch/arm64/boot/dts/freescale/imx8mq-evk.dts
> > > > +++ b/arch/arm64/boot/dts/freescale/imx8mq-evk.dts
> > > > @@ -31,6 +31,23 @@
> > > >  		gpio = <&gpio2 19 GPIO_ACTIVE_HIGH>;
> > > >  		enable-active-high;
> > > >  	};
> > > > +
> > > > +};
> > > > +
> > > > +&A53_0 {
> > > > +	cpu-supply = <&sw1a_reg>;
> > > > +};
> > > > +
> > > > +&A53_1 {
> > > > +	cpu-supply = <&sw1a_reg>;
> > > > +};
> > > > +
> > > > +&A53_2 {
> > > > +	cpu-supply = <&sw1a_reg>;
> > > > +};
> > > > +
> > > > +&A53_3 {
> > > > +	cpu-supply = <&sw1a_reg>;
> > > >  };
> > > 
> > > This should be a separate patch.
> > > 
> > 
> > OK, will send as separate patches in the next version.
> > 
> > > And AFAICS this is wrong, sw1a on the MX8M-EVK is the GPU supply,
> > > the
> > > CPU is supplied by a dedicated switcher that is controlled via a
> > > GPIO.
> > > 
> > 
> > Hmm, I think you're right. At least this is what the following
> > document says.
> > 
> > https://www.mouser.com/ds/2/302/IMX8MDQLQEVKHUG-1280333.pdf
> > 
> > So I guess this means there will not be any cpu-supply properties. 
> 
> There is a variable voltage CPU supply, but you need to model it as a
> gpio-regulator in the DT, it's not part of the PMIC provided rails.

In the schematics it's the line called PWM_LED (actually it's just
GPIO1_IO13) that controls the voltage. This changes the feedback of the
DCDC switcher, so it can toggle between 0.9V and 1.0V.

Regards,
Lucas