linux-kernel - Re: [PATCH v8 1/6] ARM: imx6q: provide documentation for new fsl,pmic-stby-poweroff property

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Date:   Fri, 27 Jul 2018 10:30:11 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Robin Gong <yibin.gong@....com>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        dl-linux-imx <linux-imx@....com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "A.s. Dong" <aisheng.dong@....com>,
        Fabio Estevam <fabio.estevam@....com>,
        Russell King <linux@...linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Leonard Crestez <leonard.crestez@....com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v8 1/6] ARM: imx6q: provide documentation for new
 fsl,pmic-stby-poweroff property

Hi Robin,

Am Freitag, den 27.07.2018, 01:51 +0000 schrieb Robin Gong:
[...]
> > > > ---
> > > >  Documentation/devicetree/bindings/clock/imx6q-clock.txt | 8 ++++++++
> > > >  1 file changed, 8 insertions(+)
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/clock/imx6q-clock.txt
> > > > b/Documentation/devicetree/bindings/clock/imx6q-clock.txt
> > > > index a45ca67a9d5f..e1308346e00d 100644
> > > > --- a/Documentation/devicetree/bindings/clock/imx6q-clock.txt
> > > > +++ b/Documentation/devicetree/bindings/clock/imx6q-clock.txt
> > > > @@ -6,6 +6,14 @@ Required properties:
> > > >  - interrupts: Should contain CCM interrupt
> > > >  - #clock-cells: Should be <1>
> > > > 
> > > > +Optional properties:
> > > > +- fsl,pmic-stby-poweroff: Configure CCM to assert PMIC_STBY_REQ
> > > > +signal
> > > > +  on power off.
> > > > +  Use this property if the SoC should be powered off by external
> > > > +power
> > > > +  management IC (PMIC) triggered via PMIC_STBY_REQ signal.
> > > 
> > > PMIC_ON_REQ didn't connect to any pin of PMIC in your case?
> > 
> > No. First, it was only one customer specific issue. After some research I found
> > even publicly available boards (for example RioTboard) which has same/similar
> > design. After seeing this in imx6 documentation as valid power off way, I have
> > no doubts - there should be even more devices doin this in the wild.
> 
> Not sure why the customer didn't follow reference design, since PMIC_ON_REQ can
> provide power off/on feature by pressing ONOFF key which connected ONOFF
> pin of i.mx6(ONOFF will toggle PMIC_ON_REQ to power off/on PMIC). The official
> power off/on way (PMIC_ON_REQ) can also power off all power rails of PFUZE except
> snvs as your patch did on PMIC_STBY_REQ.  PMIC_STBY_REQ is used to notify pmic
> switch power mode (PFM/APS) or decrease voltage to save power in kernel suspend,
> not power off....I am not sure if we need this patchset to 'workaround' the board issue.
> 
Not all boards follow the reference design, that's a fact of life.

Please look at the i.MX6Q reference manual. The sequence implemented in
this patchset can be found as a valid way to power off the system in
"60.4.3 Power mode transitions" "Normal ON to OFF with external PMIC",
so there is hardly any way to argue that this is a board specific
quirk. This is one of the Freescale/NXP recommended sequences to turn
off the system.

Regards,
Lucas