pm: add suspend_mem and suspend_standby support

[Alan Stern]

On Tue, 9 Oct 2012, Jean-Christophe PLAGNIOL-VILLARD wrote:

> > Why do you need to know the difference in your driver?  We used to
> > provide this information a long time ago, but it turned out to not be
> > needed at all and just caused problems.
> because on at91 I need to handle the mem standby at drviers level.
> 
> We do it today already by a hack in different drivers at91_udc (usb device),
> atmel_serail and at91_ohci. Those 3 IP have specifci handling when switching
> to mem pm. On at91 when switch to mem we shutdown everything and run form a slow
> clock - this is done at soc level - but those IP have issue and need specific
> care before doing so. Ohterwise when the SoC will wakeup but those IP will not
> 
> in this patch series I send the update of those 3 drivers too
> and kill the hack

How about adding a platform-specific callback routine to tell drivers 
whether or not they will run from the slow clock?  Something like:

	bool at91_suspend_will_use_slow_clock(void);

That would not involve making any changes to the driver core, and your 
three drivers could still get the information they need.

Alan Stern