On Wednesday, July 12, 2017 11:08:19 AM Florian Fainelli wrote:
> On 06/29/2017 04:00 PM, Rafael J. Wysocki wrote:
> > On Thursday, June 22, 2017 06:08:36 PM Florian Fainelli wrote:
> >> Add an optional platform_suspend_ops callback: target_state, and a
> >> helper function globally visible to get this called:
> >> platform_suspend_target_state().
> >>
> >> This is useful for platform specific drivers that may need to take a
> >> slightly different suspend/resume path based on the system's
> >> suspend/resume state being entered.
> >>
> >> Although this callback is optional and documented as such, it requires
> >> a platform_suspend_ops::begin callback to be implemented in order to
> >> provide an accurate suspend/resume state within the driver that
> >> implements this platform_suspend_ops.
> >>
> >> Signed-off-by: Florian Fainelli <f.faine...@gmail.com>
> >> ---
> >> include/linux/suspend.h | 12 ++++++++++++
> >> kernel/power/suspend.c | 15 +++++++++++++++
> >> 2 files changed, 27 insertions(+)
> >>
> >> diff --git a/include/linux/suspend.h b/include/linux/suspend.h
> >> index d9718378a8be..d998a04a90a2 100644
> >> --- a/include/linux/suspend.h
> >> +++ b/include/linux/suspend.h
> >> @@ -172,6 +172,15 @@ static inline void dpm_save_failed_step(enum
> >> suspend_stat_step step)
> >> * Called by the PM core if the suspending of devices fails.
> >> * This callback is optional and should only be implemented by
> >> platforms
> >> * which require special recovery actions in that situation.
> >> + *
> >> + * @target_state: Returns the suspend state the suspend_ops will be
> >> entering.
> >> + * Called by device drivers that need to know the platform
> >> specific suspend
> >> + * state the system is about to enter.
> >> + * This callback is optional and should only be implemented by
> >> platforms
> >> + * which require special handling of power management states within
> >> + * drivers. It does require @begin to be implemented to provide
> >> the suspend
> >> + * state. Return value is platform_suspend_ops specific, and may
> >> be a 1:1
> >> + * mapping to suspend_state_t when relevant.
> >> */
> >> struct platform_suspend_ops {
> >> int (*valid)(suspend_state_t state);
> >> @@ -184,6 +193,7 @@ struct platform_suspend_ops {
> >> bool (*suspend_again)(void);
> >> void (*end)(void);
> >> void (*recover)(void);
> >> + int (*target_state)(void);
> >
> > I would use unsigned int (the sign should not matter).
> >
> >> };
> >
> > That's almost what I was thinking about except that the values returned by
> > ->target_state should be unique, so it would be good to do something to
> > ensure that.
> >
> > The concern is as follows.
> >
> > Say you have a driver develped for platform X where ->target_state returns
> > A for "mem" and B for "standby". Then, the same IP is re-used on platform Y
> > returning B for "mem" and C for "standby" and now the driver cannot
> > distinguish between them.
> >
> > Moreover, even if they both returned A for "mem" there might be differences
> > in how "mem" was defined by each of them and therefore in what the driver
> > was
> > expected to do to handle "mem" on X and Y.
>
> That makes sense, would you need the core implementation in
> platform_suspend_target_state() to range check what
> suspend_ops->target_state() returns against a set of reserved value say,
> checking from 0 up to ACPI_S_STATE_COUNT or is there another range you
> would like to see being used?
I had an idea of using an enum type encompassing all of the power states
defined for various platforms and serving both as a registry (to ensure the
uniqueness of the values assigned to the states) and a common ground
between platforms and drivers.
Something like:
enum platform_target_state {
PLATFORM_STATE_UNKNOWN = -1,
PLATFORM_STATE_WORKING = 0,
PLATFORM_STATE_ACPI_S1,
PLATFORM_STATE_ACPI_S2,
PLATFORM_STATE_ACPI_S3,
PLATFORM_STATE_MY_BOARD_1_GATE_CLOCKS,
PLATFORM_STATE_MY_BOARD_1_GATE_POWER,
PLATFORM_STATE_ANOTHER_BOARD_DO_CRAZY_STUFF,
...
};
and define ->target_state to return a value of this type.
Then, if a driver sees one of these and recognizes that value, it should
know exactly what to do.
Thanks,
Rafael
