From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [PATCH v5 01/48] kernel: Add support for power-off handler call chain Date: Thu, 6 Nov 2014 14:27:03 -0800 Message-ID: <20141106222703.GA6377@roeck-us.net> References: <1415292213-28652-1-git-send-email-linux@roeck-us.net> <1415292213-28652-2-git-send-email-linux@roeck-us.net> <3183593.9HaIZKjCKr@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from bh-25.webhostbox.net ([208.91.199.152]:40330 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751020AbaKFW1L (ORCPT ); Thu, 6 Nov 2014 17:27:11 -0500 Received: from mailnull by bh-25.webhostbox.net with sa-checked (Exim 4.82) (envelope-from ) id 1XmVWI-002ddz-NW for linux-pm@vger.kernel.org; Thu, 06 Nov 2014 22:27:10 +0000 Content-Disposition: inline In-Reply-To: <3183593.9HaIZKjCKr@vostro.rjw.lan> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "Rafael J. Wysocki" Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Alan Cox , Alexander Graf , Andrew Morton , Geert Uytterhoeven , Heiko Stuebner , Lee Jones , Len Brown , Pavel Machek , Philippe =?iso-8859-1?Q?R=E9tornaz?= , Romain Perier On Thu, Nov 06, 2014 at 11:30:59PM +0100, Rafael J. Wysocki wrote: > On Thursday, November 06, 2014 08:42:45 AM Guenter Roeck wrote: > > Various drivers implement architecture and/or device specific means= to > > power off the system. For the most part, those drivers set the glo= bal > > variable pm_power_off to point to a function within the driver. > >=20 > > This mechanism has a number of drawbacks. Typically only one schem= e > > to remove power is supported (at least if pm_power_off is used). > > At least in theory there can be multiple means remove power, some o= f > > which may be less desirable. For example, some mechanisms may only > > power off the CPU or the CPU card, while another may power off the > > entire system. Others may really just execute a restart sequence > > or drop into the ROM monitor. Using pm_power_off can also be racy > > if the function pointer is set from a driver built as module, as th= e > > driver may be in the process of being unloaded when pm_power_off is > > called. If there are multiple power-off handlers in the system, rem= oving > > a module with such a handler may inadvertently reset the pointer to > > pm_power_off to NULL, leaving the system with no means to remove po= wer. > >=20 > > Introduce a system power-off handler call chain to solve the descri= bed > > problems. This call chain is expected to be executed from the arch= itecture > > specific machine_power_off() function. Drivers and architeceture c= ode > > providing system power-off functionality are expected to register w= ith > > this call chain. When registering a power-off handler, callers can > > provide a priority to control power-off handler execution sequence > > and thus ensure that the power-off handler with the optimal capabil= ities > > to remove power for a given system is called first. > >=20 > > Cc: Alan Cox > > Cc: Alexander Graf > > Cc: Andrew Morton > > Cc: Geert Uytterhoeven > > Cc: Heiko Stuebner > > Cc: Lee Jones > > Cc: Len Brown > > Cc: Pavel Machek > > Cc: Philippe R=E9tornaz > > Cc: Rafael J. Wysocki > > Cc: Romain Perier > > Acked-by: Pavel Machek > > Acked-by: Heiko Stuebner > > Signed-off-by: Guenter Roeck > > --- > > v5: > > - Rebase to v3.18-rc3 > > v4: > > - Do not use notifiers but internal functions and data structures t= o manage > > the list of power-off handlers. Drop unused parameters from callb= acks, and > > make the power-off function type void. > > Code to manage and walk the list of callbacks is derived from not= ifier.c. > > v3: > > - Rename new file to power_off_handler.c > > - Replace poweroff in all newly introduced variables and in text > > with power_off or power-off as appropriate > > - Replace POWEROFF_PRIORITY_xxx with POWER_OFF_PRIORITY_xxx > > - Execute power-off handlers without any locks held > > v2: > > - poweroff -> power_off > > - Add defines for default priorities > > - Use raw notifiers protected by spinlocks instead of atomic notifi= ers > > - Add register_poweroff_handler_simple > > - Add devm_register_power_off_handler > >=20 > > include/linux/pm.h | 28 ++++ > > kernel/power/Makefile | 1 + > > kernel/power/power_off_handler.c | 293 +++++++++++++++++++++++++++= ++++++++++++ > > 3 files changed, 322 insertions(+) > > create mode 100644 kernel/power/power_off_handler.c > >=20 > > diff --git a/include/linux/pm.h b/include/linux/pm.h > > index 383fd68..a4d6bf8 100644 > > --- a/include/linux/pm.h > > +++ b/include/linux/pm.h > > @@ -35,6 +35,34 @@ extern void (*pm_power_off)(void); > > extern void (*pm_power_off_prepare)(void); > > =20 > > struct device; /* we have a circular dep with device.h */ > > + > > +/* > > + * Data structures and callbacks to manage power-off handlers > > + */ > > + > > +struct power_off_handler_block { > > + void (*handler)(struct power_off_handler_block *); > > + struct power_off_handler_block __rcu *next; > > + int priority; > > +}; > > + > > +int register_power_off_handler(struct power_off_handler_block *); > > +int devm_register_power_off_handler(struct device *, > > + struct power_off_handler_block *); > > +int register_power_off_handler_simple(void (*function)(void), int = priority); > > +int unregister_power_off_handler(struct power_off_handler_block *)= ; > > +void do_kernel_power_off(void); > > +bool have_kernel_power_off(void); > > + > > +/* > > + * Pre-defined power-off handler priorities > > + */ > > +#define POWER_OFF_PRIORITY_FALLBACK 0 > > +#define POWER_OFF_PRIORITY_LOW 64 > > +#define POWER_OFF_PRIORITY_DEFAULT 128 > > +#define POWER_OFF_PRIORITY_HIGH 192 > > +#define POWER_OFF_PRIORITY_HIGHEST 255 >=20 > I'm not sure why we need these gaps in the priority space. >=20 > I guess it might be possible to use >=20 > enum power_off_priority { > POWER_OFF_PRIORITY_FALLBACK =3D 0, > POWER_OFF_PRIORITY_LOW, > POWER_OFF_PRIORITY_DEFAULT, > POWER_OFF_PRIORITY_HIGH, > POWER_OFF_PRIORITY_HIGHEST, > POWER_OFF_PRIORITY_LIMIT, > }; I retained the large number space on purpose, specifically to permit in= -between priorities. In other words, I want people to be able to say "priority f= or this handler is higher than low but lower than default". After all, the defi= nes were intended as hints, not as a "Thou shall use those and only those priori= ties". Having said that, the important part is to get the series accepted, so = I won't argue if that is what it takes to get an Ack. Let me know. Thanks, Guenter >=20 > and then make register_ complain if priority is POWER_OFF_PRIORITY_LI= MIT > or greater. >=20 > But I'm OK with the rest, so if no one else sees a problem here, > I'm not going to make a fuss about it. >=20 > Rafael >=20