[PATCH 5/5] ARM: OMAP3: Update clocksource timer selection

[Bedia, Vaibhav]

Hi Jon,

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

[...]
>  
>  #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?

Regards,
Vaibhav