On Mon, Mar 19, 2012 at 17:14:30, Ming Lei wrote: > On Mon, Mar 19, 2012 at 7:11 PM, Hiremath, Vaibhav <hvaibhav@xxxxxx> wrote: > > > > I think you made very good point here. With the above patch, we are almost missing the capability of registering dmtimer as a clocksource for OMAP. > > It will always use 32k-counter, and never fall back to dmtimer. > > > > Then the only options we have here is, > > > > 1) Register both the timers, 32k-counter and dmtimer for clocksource; let > > Kernel pick up best rating clocksource out of these two. > > > > In case of OMAP1/2/3/4, kernel will use dmtimer, since it has better > > Rating. User can choose the 32k-counter clocksource via bootargs. > > > > Impact: without bootargs for clocksource selection, kernel will choose > > dmtimer, impacting loss of time during suspend/resume. > > > > > > 2) Let the current code be as is, means, the clocksource registration will > > Happened based on "#ifdef CONFIG_OMAP_32K_TIMER" and this option > > selection will be Controlled by Kconfig rules. > > How about the 3rd option? > > 3), take the way in your patch 1) at default, but will switch to > register dmtimer > directly and bypass 32k-counter if user need it via kernel parameter. > > As far as I can think of, the situations required for dmtimer are high-frequency > perf sample and high precision trace points, so looks it is OK to take > 32k-counter > at default. > But if you register both the timers (dmtimer & 32ksync), then initially kernel will only pick up dmtimer, as this has better rating. And late in the boot sequence clocksource switch will happen, base on kernel parameter (clocksource=). So logically dmtimer will be always used as a default here. Thanks, Vaibhav > Thanks, > -- > Ming Lei > -- 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
