On Wednesday, 27 June 2007 22:41, David Brownell wrote: > On Monday 25 June 2007, Rafael J. Wysocki wrote: > > From: Rafael J. Wysocki <rjw@xxxxxxx> > > > > The at91 platform code incorrectly assumes that pm_ops->prepare() will be called > > Make that "code assumes that ... but that requirement was broken > by a patch merged in RC5 to make ACPI behave better." That is, > the problem is not that the AT91 code was doing anything wrong, > it's that the API definition changed (incompatibly!) in RC5. > > > before devices are suspended and uses it to make the PM core set the target > > system sleep state used by the platform when suspending devices. Thus, at91 > > needs a new member function in 'struct pm_ops' that will be used by the PM core > > to convey the target system sleep state to the platform code before devices are > > suspended. > > > > Moreover, in the future some drivers may need to use ACPI to determine the low > > power states in which to place their devices, but to provide the drivers with > > this information the ACPI core needs to know what sleep state the system is > > going to enter. Namely, the device's state should not be too high power for > > given system sleep state and, if the device is supposed to be able to wake up > > the system, its state should not be too low power for the wake up to be > > possible). However, pm_ops->prepare() is only called after the drivers' > > .suspend() callbacks have been executed, so we need an additional means to > > convey the target system sleep state to the ACPI core. The new member function > > in 'struct pm_ops', set_target(), can be used for this purpose. > > That's all extremely verbose: (a) prepare() used to be called > early, so a platform knew the target state while devices were > being suspended; (b) that changed in RC5; (c) we still need a > call delivering the original semantics, since (c1) AT91 depends > on it now and (c2) ACPI should be depending on it, and this change > broke a patch fixing that; ... so (d) here's a patch adding a new > function that can do what prepare() used to do. OK, I'll modify the changelog. > > > > Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx> > > Acked-by: David Brownell <dbrownell@xxxxxxxxxxxxxxxxxxxxx> Thanks, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
