Re: [PATCH v5 3/6] kernel/reboot.c: export pm_power_off_prepare

From	Oleksij Rempel <ore@pengutronix.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH v5 3/6] kernel/reboot.c: export pm_power_off_prepare
Date	2017-06-20 17:40 +0200
Message-ID	<tUtq2-1Y8-27@gated-at.bofh.it> (permalink)
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On Tue, Jun 20, 2017 at 05:37:06PM +0300, Leonard Crestez wrote:
> On Tue, 2017-06-20 at 07:01 +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:
> > > > 
> > > > Export pm_power_off_prepare. It is needed to implement power off on
> > > > Freescale/NXP iMX6 based boards with external power management
> > > > integrated circuit (PMIC).
> > > > 
> > > > Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> > > > ---
> > > >  kernel/reboot.c | 1 +
> > > >  1 file changed, 1 insertion(+)
> > > > 
> > > > diff --git a/kernel/reboot.c b/kernel/reboot.c
> > > > index bd30a973fe94..a6903bf772c7 100644
> > > > --- a/kernel/reboot.c
> > > > +++ b/kernel/reboot.c
> > > > @@ -49,6 +49,7 @@ int reboot_force;
> > > >   */
> > > > 
> > > >  void (*pm_power_off_prepare)(void);
> > > > +EXPORT_SYMBOL(pm_power_off_prepare);
> > > > 
> > > Could you register a reboot notifier in the pfuze driver instead? Right
> > > now the only user of pm_power_off_prepare is ACPI so this alternative
> > > seems less intrusive.
> > hm... in this case i will need to make sure that reboot handler is not 
> > executed on reboot. This will make code looks strange. Which is opposite 
> > of your comment in other email about strange standby code for power off :)
> > Should i really do this?
> 
> A reboot handler receives a parameter to differentiate between reboot
> and shutdown so it would be easy. Isn't it preferable to use an
> existing mechanism instead of exporting a new symbol?
> 
> But maybe somebody else will Ack this, I don't particularly insist on
> changing this.

I just need to make sure, nothing else will do some thing unexpected
with PMIC. Don't forget we use same PMIC_STBY_REQ signal for stanby,
suspend to RAM and for power off. Entering wrong state in wrong moment
will be fatal. This is why I use last possible step before pm_power_off.

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Re: [PATCH v5 3/6] kernel/reboot.c: export pm_power_off_prepare Oleksij Rempel <ore@pengutronix.de> - 2017-06-20 07:10 +0200
  Re: [PATCH v5 3/6] kernel/reboot.c: export pm_power_off_prepare Oleksij Rempel <ore@pengutronix.de> - 2017-06-20 17:40 +0200

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