Re: [linux-pm] [RFC] Add some hooks to generic suspend code

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Tue, 2005-05-31 at 12:13 +0200, Pavel Machek wrote:
> Hi!
> 
> > While consolidating the powermac suspend to ram and suspend to disk
> > implementations to properly use the new framework in kernel/power, among
> > others, I ended up with the need of adding various callbacks to
> > kernel/power/main.c. Here is a patch adding & documenting those.
> > 
> > The reasons I need them are:
> > 
> > 	/* Call before process freezing. If returns 0, then no freeze
> > 	 * should be done, if 1, freeze, negative -> error
> > 	 */
> > 	int (*pre_freeze)(suspend_state_t state);
> > 
> > I'm using that one for calling my "old style" notifiers (they are beeing phased
> > out but I still have a couple of drivers using them). The reason I do that here
> > is because that's how my APM emulation hooks, and that code interacts with userland
> > (to properly signal things like X of the suspend process), so I need to do that
> > before we freeze processes.
> 
> This should not be needed in future, right? Could it be marked
> deprecated or something?

Not really ... I need to notify userland before we freeze processes.

> > 	/* called after sysdevs and "irq off" devices have been
> > 	 * worken up, irqs have just been restored to whatever state
> > 	 * prepare_irqs() left them in.
> > 	 */
> > 	void (*finish_irqs)(suspend_state_t state);
> > 
> > This is the pending of the above callback. It gets called after sysdev's
> > have been woken up but before normal devices have. It's called after the core has
> > restored local interrupts to what they were upon exit of prepare_irqs(), so if
> > you do nothing special in prepare_irqs(), you'll get entered with irqs re-enabled
> > here, while if you exit prepare_irqs() with irqs off, you'll get here with irqs
> > off as well (and thus become responsible for re-enabling them).
> > 
> > I want this callback to have finer control of re-enabling interrutps. The interrupt
> > controller has been partially reconfigured earlier in arch code, but the CPU priority
> > is only lowered here, so that it starts hitting the CPU again only now. There is
> > also some code to properly wake up the CPU decrementer so it ticks right away, and
> > to force taking a pseudo-interrupt (to sort-of "kick" the interrupt controller into
> > life, seems to work around an issue that I think is related to a HW bug in the
> > interrupt controller we use). 
> 
> Could you simply reconfigure interrupt controller fully in earlier arch code?

Nope, it has to happen between device_suspend, ant device_power_off.
Basically, I need control around the time we switch irqs off.

> > 	/* called after unfreezing userland */
> > 	void (*post_freeze)(suspend_state_t state);
> > 
> > That one is the mirror of pre-freeze, gets called after userland has been re-enabled,
> > it also calls my old-style notifiers, which includes APM emulation, which is important
> > for sending the APM wakeup events to things like X.
> 
> Could this be marked deprecated, too?
> 
> Alternatively, proper way of notifying X (etc) should be created, and
> done from generic code....

Sure, ideally. However, existing X knows how to deal with APM events,
and thus APM emulation is an important thing to get something that
works. Pne thing I should do is consolidate PPC APM emu with ARM one as
I think Russell improve my stuff significantly.

Ben.