Subject: [PATCH v4 03/11] ARM: OMAP2+: timer: Add suspend-resume callbacks for clkevent device

From: [email-masked] (Tony Lindgren)
Date: Mon, 14 Jul 2014 23:48:08 -0700

* Dave Gerlach <[email-masked]> [140714 10:44]:
> Santosh, Tony,
> 
> On 07/14/2014 09:37 AM, Santosh Shilimkar wrote:
> >On Monday 14 July 2014 07:15 AM, Tony Lindgren wrote:
> >>* Dave Gerlach <[email-masked]> [140710 19:59]:
> >>>From: Vaibhav Bedia <[email-masked]>
> >>>
> >>>OMAP timer code registers two timers - one as clocksource
> >>>and one as clockevent. Since AM33XX has only one usable timer
> >>>in the WKUP domain 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 <[email-masked]>
> >>>Signed-off-by: Dave Gerlach <[email-masked]>
> >>>---
> >>>v3->v4:
> >>>	Only use for am33xx soc now.
> >>>
> >>>  arch/arm/mach-omap2/timer.c | 28 ++++++++++++++++++++++++++++
> >>>  1 file changed, 28 insertions(+)
> >>>
> >>>diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c
> >>>index 43d03fb..6fc1748 100644
> >>>--- a/arch/arm/mach-omap2/timer.c
> >>>+++ b/arch/arm/mach-omap2/timer.c
> >>>@@ -128,6 +128,29 @@ static void omap2_gp_timer_set_mode(enum clock_event_mode mode,
> >>>  	}
> >>>  }
> >>>
> >>>+static void omap_clkevt_suspend(struct clock_event_device *unused)
> >>>+{
> >>>+	struct omap_hwmod *oh;
> >>>+
> >>>+	oh = omap_hwmod_lookup(clockevent_gpt.name);
> >>>+	if (!oh)
> >>>+		return;
> >>>+
> >>>+	omap_hwmod_idle(oh);
> >>>+}
> >>>+
> >>>+static void omap_clkevt_resume(struct clock_event_device *unused)
> >>>+{
> >>>+	struct omap_hwmod *oh;
> >>>+
> >>>+	oh = omap_hwmod_lookup(clockevent_gpt.name);
> >>>+	if (!oh)
> >>>+		return;
> >>>+
> >>>+	omap_hwmod_enable(oh);
> >>>+	__omap_dm_timer_int_enable(&clkev, OMAP_TIMER_INT_OVERFLOW);
> >>>+}
> >>>+
> >>
> >>This is going to make moving the timer code into drivers one step
> >>tougher to do. And you don't need to look up the hwmod entry every
> >>time, just initialize it during the init.
> 
> Yes you are right about looking up only at init I need to change that. I
> agree that this makes moving the timers harder but I'm not sure there's any
> way around this. I attempted to use the omap_device layer here but there is
> no device at all created here, it does not hook into the normal PM layer
> through omap_device. This clock must be shut off as it sits in the
> peripheral power domain and any active clock within the domain will prevent
> suspend from happening, so we end up with a platform specific issue here. It
> seems that the only way I can get to the clock is through the hwmod.

It's best to register these kind of functions as platform_data
in pdata-quirks.c auxdata. That way when this moves to live
in drivers/clocksource the driver does not need to know anything
about the interconnect specific registers.

Also, please don't use Linux generic names here.. Maybe use
omap_clkevt_idle/unidle? The linux suspend and resume hooks
and runtime PM could all use these functions then.

> >>>+	if (soc_is_am33xx()) {
> >>>+		clockevent_gpt.suspend = omap_clkevt_suspend;
> >>>+		clockevent_gpt.resume = omap_clkevt_resume;
> >>>+	}
> >>>+
> >>
> >>Maybe try to set up things so we initialize the SoC specific
> >>timer suspend and resume functions in mach-omap2/timer.c
> >>in a way where eventually the device driver can easily use
> >>them?
> >>
> >+1. I had similar comments on the previous version too.
> 
> This was my attempt to make things specific to only am335x based on
> Santosh's previous comments as last time they were populated for every
> device even when unneeded. These are not standard suspend/resume handlers,
> they are specific to clock event. I know there will always need to be at
> least some code here for the early timer init based on previous timer
> cleanup series I've seen, so perhaps I could hook it in there when the time
> comes?

Well just adding a minimal include/linux/platform_data/timer-omap.h
to pass those function pointers to the driver should do the trick.

Regards,

Tony