Subject: [PATCH 12/15] ARM: OMAP: timer: Add suspend-resume callbacks for clockevent device

From: [email-masked] (Santosh Shilimkar)
Date: Sat, 3 Nov 2012 21:22:04 +0530

On Friday 02 November 2012 06:02 PM, Vaibhav Bedia wrote:
> From: Vaibhav Hiremath <[email-masked]>
>
> The current OMAP timer code registers two timers -
> one as clocksource and one as clockevent.
Actually OMAP also uses only one timer. The clocksource
is taken care by 32K syntimer till OMAP4 and by realtime
counter on OMAP5. There is a clocksource registration of
timer is available but that is not being used in systems.

> 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.
>
So you use WKUP domain timer for clocksource and PER
domain one for clock-event ?

> Signed-off-by: Vaibhav Hiremath <[email-masked]>
> Signed-off-by: Vaibhav Bedia <[email-masked]>
> ---
>   arch/arm/mach-omap2/timer.c |   31 +++++++++++++++++++++++++++++++
>   1 files changed, 31 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c
> index 6584ee0..e8781fd 100644
> --- a/arch/arm/mach-omap2/timer.c
> +++ b/arch/arm/mach-omap2/timer.c
> @@ -135,6 +135,35 @@ 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", 2);
> +	oh = omap_hwmod_lookup(name);
> +	if (!oh)
> +		return;

You can move all the look up stuff in init code and then
suspend resume hooks will be cleaner.
> +
> +	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", 2);
> +	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);
> +}
> +
OK. So since your clk_event stops when PER idles, how do you plan
to support the SOC idle. For CPUIDLE path, you need your clock-event
to wakeup the system based on next timer expiry. So you need your
clock event to be active. Indirectly, you can't let PER idle which
leads npo CORE idle->SOC idle.

How do you plan to address this ? Os is SOC idle is not suppose
to be added for AMXXX ?

Regards
Santosh