linux-kernel - Re: [PATCH v5 2/6] ARM: imx6: register pm_power_off handler if "fsl,pmic-stby-poweroff" is set

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Date:   Tue, 20 Jun 2017 17:25:31 +0200
From:   Oleksij Rempel <ore@...gutronix.de>
To:     Leonard Crestez <leonard.crestez@....com>
Cc:     Oleksij Rempel <o.rempel@...gutronix.de>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>, linux-kernel@...r.kernel.org,
        Mark Brown <broonie@...nel.org>, kernel@...gutronix.de,
        Fabio Estevam <fabio.estevam@....com>,
        Russell King <linux@...linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shawn Guo <shawnguo@...nel.org>, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v5 2/6] ARM: imx6: register pm_power_off handler if
 "fsl,pmic-stby-poweroff" is set

On Tue, Jun 20, 2017 at 05:32:16PM +0300, Leonard Crestez wrote:
> On Tue, 2017-06-20 at 06:55 +0200, Oleksij Rempel wrote:
> > On 19.06.2017 13:35, Leonard Crestez wrote:
> > > On Mon, 2017-06-19 at 07:02 +0200, Oleksij Rempel wrote:
> > > > 
> > > > One of the Freescale recommended sequences for power off with
> > > > external
> > > > PMIC is the following:
> > > > ...
> > > > 3.  SoC is programming PMIC for power off when standby is asserted.
> > > > 4.  In CCM STOP mode, Standby is asserted, PMIC gates SoC supplies.
> > > > 
> > > > This patch implements step 4. of this sequence.
> > > > 
> > > > Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> > > > ---
> > > >  arch/arm/mach-imx/pm-imx6.c | 25 +++++++++++++++++++++++++
> > > >  1 file changed, 25 insertions(+)
> > > > 
> > > > diff --git a/arch/arm/mach-imx/pm-imx6.c b/arch/arm/mach-imx/pm-
> > > > imx6.c
> > > > index e61b1d1027e1..cb76832935f0 100644
> > > > --- a/arch/arm/mach-imx/pm-imx6.c
> > > > +++ b/arch/arm/mach-imx/pm-imx6.c
> > > > @@ -602,6 +602,28 @@ static void __init imx6_pm_common_init(const
> > > > struct imx6_pm_socdata
> > > >  				   IMX6Q_GPR1_GINT);
> > > >  }
> > > > 
> > > > +static void imx6_pm_poweroff(void)
> > > > +{
> > > > +	imx6_set_lpm(STOP_POWER_OFF);
> > > > +	cpu_suspend(0, imx6q_suspend_finish);
> > > It's a bit strange that you're using parts of the suspend code for
> > > this. Perhaps you could just write your bits to CLPCR and then execute
> > > a WFI?
> > Well, every thing in this patch set, yell about using standby/suspend 
> > path in HW for power off. Even iMX code use STOP_POWER_OFF for 
> > configuring this regs. How can it be more strange? :) Should i really 
> > duplicate code to hide this?
> > 
> This code is used to set the power state the soc enters on WFI. These
> function try to ensure that it is possible to come back up when woken
> by an interrupt later. That part you don't want, right?
> 
> However I can't think of any obvious way this could misbehave so I
> guess it's fine.

ok, thx.

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