RE: [RFC v2 12/18] ARM: OMAP2+: timer: Add suspend-resume callbacks for clockevent device

["Bedia, Vaibhav" <vaibhav.bedia@ti.com>]

On Fri, Jan 18, 2013 at 10:55:43, Shilimkar, Santosh wrote:
> On Friday 18 January 2013 12:15 AM, Jon Hunter wrote:
> >
> > On 01/10/2013 10:37 PM, Bedia, Vaibhav wrote:
> >> On Tue, Jan 08, 2013 at 20:45:10, Shilimkar, Santosh wrote:
> >>> On Monday 31 December 2012 06:37 PM, Vaibhav Bedia wrote:
> >>>> The current OMAP timer code registers two timers -
> >>>> one as clocksource and one as clockevent.
> >>>> AM33XX has only one usable timer in the WKUP domain
> >>>> so one of the timers needs suspend-resume support
> >>>> to restore the configuration to pre-suspend state.
> >>>>
> >>>> commit adc78e6 (timekeeping: Add suspend and resume
> >>>> of clock event devices) introduced .suspend and .resume
> >>>> callbacks for clock event devices. Leverages these
> >>>> callbacks to have AM33XX clockevent timer which is
> >>>> in not in WKUP domain to behave properly across system
> >>>> suspend.
> >>>>
> >>>> Signed-off-by: Vaibhav Bedia <vaibhav.bedia@ti.com>
> >>>> Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
> >>>> Cc: Benoit Cousson <b-cousson@ti.com>
> >>>> Cc: Paul Walmsley <paul@pwsan.com>
> >>>> Cc: Kevin Hilman <khilman@deeprootsystems.com>
> >>>> Cc: Vaibhav Hiremath <hvaibhav@ti.com>
> >>>> Cc: Jon Hunter <jon-hunter@ti.com>
> >>>> ---
> >>>> v1->v2:
> >>>> 	Get rid of harcoded timer id.
> >>>> 	Note: since a platform device is not created for these timer
> >>>> 	instances and because there's very minimal change needed for
> >>>> 	restarting the timer a full blown context save and restore
> >>>> 	has been skipped.
> >>>>
> >>>>    arch/arm/mach-omap2/timer.c |   33 +++++++++++++++++++++++++++++++++
> >>>>    1 files changed, 33 insertions(+), 0 deletions(-)
> >>>>
> >>>> diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c
> >>>> index 691aa67..38f9cbc 100644
> >>>> --- a/arch/arm/mach-omap2/timer.c
> >>>> +++ b/arch/arm/mach-omap2/timer.c
> >>>> @@ -128,6 +128,36 @@ static void omap2_gp_timer_set_mode(enum clock_event_mode mode,
> >>>>    	}
> >>>>    }
> >>>>
> >>>> +static void omap_clkevt_suspend(struct clock_event_device *unused)
> >>>> +{
> >>>> +	char name[10];
> >>>> +	struct omap_hwmod *oh;
> >>>> +
> >>>> +	sprintf(name, "timer%d", clkev.id);
> >>>> +	oh = omap_hwmod_lookup(name);
> >>>> +	if (!oh)
> >>>> +		return;
> >>>> +
> >>>> +	__omap_dm_timer_stop(&clkev, 1, clkev.rate);
> >>>> +	omap_hwmod_idle(oh);
> >>>> +}
> >>>> +
> >>>> +static void omap_clkevt_resume(struct clock_event_device *unused)
> >>>> +{
> >>>> +	char name[10];
> >>>> +	struct omap_hwmod *oh;
> >>>> +
> >>>> +	sprintf(name, "timer%d", clkev.id);
> >>>> +	oh = omap_hwmod_lookup(name);
> >>>> +	if (!oh)
> >>>> +		return;
> >>>> +
> >>>> +	omap_hwmod_enable(oh);
> >>>> +	__omap_dm_timer_load_start(&clkev,
> >>>> +			OMAP_TIMER_CTRL_ST | OMAP_TIMER_CTRL_AR, 0, 1);
> >>>> +	__omap_dm_timer_int_enable(&clkev, OMAP_TIMER_INT_OVERFLOW);
> >>>> +}
> >>>> +
> >>> Am still bit uncomfortable with direct hwmod usage in the suspend/resmue
> >>> hooks.
> >>>
> >>> Jon, Any alternatives you can think of ?
> >>>
> >>
> >> Jon,
> >>
> >> Any suggestions here?
> >
> > Sorry completed this missed this!
> >
> > Unfortunately, I don't have any good suggestions here. However, I am
> > wondering if the suspend/resume handlers can just be calls to
> > omap_hwmod_idle/enable and we can remove these __omap_dm_timer_xxxx
> > calls (I don't think they are needed). Furthermore, my understanding is
> > this is only needed for AM335x (per the changelog), and so we should not
> > add suspend/resume handlers for all OMAP2+ based devices.
> >
> I agree with the direction.
> 

I need to retain the call to enable the interrupt but the others can be dropped.
Will take care of this and the comment on invoking the suspend/resume handlers
only for AM335x in the next version.

Regards,
Vaibhav