On 02/01/2013 02:59 AM, Jon Hunter wrote: > > On 02/01/2013 02:41 AM, Bedia, Vaibhav wrote: >> 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 :) > > Thanks. > >> [...] >>> >>> #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 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
