linux-kernel - RE: [PATCH] ARM: dts: imx6: correct anatop regulators range

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Date:   Fri, 29 Jun 2018 08:41:52 +0000
From:   Anson Huang <anson.huang@....com>
To:     Lucas Stach <l.stach@...gutronix.de>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH] ARM: dts: imx6: correct anatop regulators range

Hi, Lucas

Anson Huang
Best Regards!


> -----Original Message-----
> From: Lucas Stach [mailto:l.stach@...gutronix.de]
> Sent: Friday, June 29, 2018 4:39 PM
> To: Anson Huang <anson.huang@....com>; shawnguo@...nel.org;
> s.hauer@...gutronix.de; kernel@...gutronix.de; Fabio Estevam
> <fabio.estevam@....com>; robh+dt@...nel.org; mark.rutland@....com;
> linux-arm-kernel@...ts.infradead.org; devicetree@...r.kernel.org;
> linux-kernel@...r.kernel.org
> Cc: dl-linux-imx <linux-imx@....com>
> Subject: Re: [PATCH] ARM: dts: imx6: correct anatop regulators range
> 
> Am Freitag, den 29.06.2018, 08:27 +0000 schrieb Anson Huang:
> > Hi, Lucas
> >
> > Anson Huang
> > Best Regards!
> >
> >
> > > -----Original Message-----
> > > > > From: Lucas Stach [mailto:l.stach@...gutronix.de]
> > > Sent: Friday, June 29, 2018 4:15 PM
> > > > > > > To: Anson Huang <anson.huang@....com>; shawnguo@...nel.org;
> > > > > s.hauer@...gutronix.de; kernel@...gutronix.de; Fabio Estevam
> > > > > > > > > <fabio.estevam@....com>; robh+dt@...nel.org;
> > > > > > > > > mark.rutland@....com;
> > > > > linux-arm-kernel@...ts.infradead.org;
> > > > > devicetree@...r.kernel.org;
> > > linux-kernel@...r.kernel.org
> > > > > Cc: dl-linux-imx <linux-imx@....com>
> > > Subject: Re: [PATCH] ARM: dts: imx6: correct anatop regulators range
> > >
> > > Am Freitag, den 29.06.2018, 15:54 +0800 schrieb Anson Huang:
> > > > Correct some i.MX6 SoCs anatop regulators range according to
> > > > reference manual.
> > > >
> > > > Signed-off-by: Anson Huang <Anson.Huang@....com>
> > >
> > > NACK.
> > >
> > > This is wrong. While the regulator supports this range, the SoC
> > > doesn't. The current settings are derived from the allowed operating
> > > ranges of the SoC (at least for the MX6QDL), which is in accordance
> > > with how regulator constraints in DT are meant to be used.
> >
> >
> > Understand that normally these regulators' voltage are NOT adjusted,
> > we just use the default value, let's just call the operating range of
> > the SoC "SoC range", my intention is to make all i.MX6's anatop
> > regulator settings aligned since they are in same series, I saw some
> > i.MX6 SoCs use same SoC range as anatop ldo range, but some are NOT,
> > like imx6qdl/imx6sx/imx6sl use different SoC range than anatop ldo
> > range, but imx6ul/ull/sll use same regulator range as anatop ldo, and
> > regulator 1p1/2p5/3p0 also have different settings, some are use SoC range
> and some are just same as anatop ldo range....this looks really confused.
> >
> > So, do you think we can adjust the imx6ul/ull/sll's regulator range to
> > be SoC range rather than anatop ldo range? And how to define the SoC
> > range? Like the 1p1 ldo range, how do we know which range is fine? As I saw
> it is 1v ~ 1.2v on imx6qdl, but 0.8v ~ 1.375v on imx6sl?
> 
> If you want to align those voltages to something then it's definitely the SoC
> range you want to use. This is how the constraints are specified in the DT
> binding, as being the allowed voltage range that won't damage any of the
> attached consumers.
> 
> Please align the constraints to the operating ranges, as specified in the
> datasheet. For example an excerpt from the i.MX6SL datasheet:
> 
> "4.3.2.1 Regulators for Analog Modules
>   LDO_1P1
>    [...] Typical Programming Operating Range is 1.0 V to 1.2 V with the
> nominal default setting as 1.1 V"
> 
> So the range for 1p1 LDO on i.MX6SL should be 1.0V to 1.2V, which is the same
> as i.MX6QDL.

OK, thanks, I will check all the datasheet and rework a patch.

Anson.

> 
> Regards,
> Lucas