On 02/01/2013 02:59 AM, Jon Hunter wrote:

On 02/01/2013 02:41 AM, Bedia, Vaibhav wrote:

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Hi Jon,

On Wed, Jan 30, 2013 at 22:34:31, Hunter, Jon wrote:

quoted

When booting with device-tree for OMAP3 and AM335x devices and a gptimer
is used as the clocksource (which is always the case for AM335x), a
gptimer located in a power domain that is not always-on is selected.
Ideally we should use a gptimer located in a power domain that is always
on (such as the wake-up domain) so that time can be maintained during a
kernel suspend without keeping on additional power domains unnecessarily.

In order to fix this so that we can select a gptimer located in a power
domain that is always-on, the following changes were made ...
1. Currently, only when selecting a gptimer to use for a clockevent
   timer, do we pass a timer property that can be used to select a
   specific gptimer. Change this so that we can pass a property when
   selecting a gptimer to use for a clocksource timer too.
2. Currently, when selecting either a gptimer to use for a clockevent
   timer or a clocksource timer and no timer property is passed, then
   the first available timer is selected regardless of the properties
   it has. Change this so that if no properties are passed, then a timer
   that does not have additional features (such as always-on, dsp-irq,
   pwm, and secure) is selected.

Please note that using a gptimer for both clocksource and clockevents
can have a system power impact during idle. The reason being is that
OMAP and AMxxx devices typically only have one gptimer in a power domain
that is always-on. Therefore when the kernel is idle both the clocksource
and clockevent timers will be active and this will keep additional power
domains on. During kernel suspend, only the clocksource timer is active
and therefore, it is better to use a gptimer in a power domain that is
always-on for clocksource.

It's always a pleasure reading the changelog in your patches :)

Thanks.

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[...]

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 #if defined(CONFIG_ARCH_OMAP3) || defined(CONFIG_SOC_AM33XX)
-OMAP_SYS_GP_TIMER_INIT(3, 1, "timer_sys_ck", "ti,timer-alwon",
-		       2, "timer_sys_ck");
+OMAP_SYS_GP_TIMER_INIT(3, 2, "timer_sys_ck", NULL,
+		       1, "timer_sys_ck", "ti,timer-alwon");
 #endif

Minor point... was the intention of changing of clkev_nr and clksrc_nr to make
it consistent with what happens on AM33xx which is DT-only?

I don't see this as being DT specific. It is more of a policy change to
ensure a wake-up domain timer is used for clocksource when we are using
gptimers for both clocksource and clockevents. It was your patch for
AM335x that made me see the need for this, if that makes sense. May be I
should have referenced that in the changelog.

Sorry to be clear, I don't see the policy change as DT specific.

In answer to your question, yes clkev_nr and clksrc_nr are changed so
the policy it is consistent regardless of whether you use DT or not. In
other words, an OMAP3 board using a gptimer for clocksource  (such as
cm-t3517) and does not use DT, would work the same as AM335x with DT.

Cheers
Jon