On Thu, 2012-07-26 at 10:44 -0700, Kevin Hilman wrote: > Rajendra Nayak <rnayak@xxxxxx> writes: > > > On Thursday 26 July 2012 04:13 AM, Kevin Hilman wrote: > >> Tero Kristo<t-kristo@xxxxxx> writes: > >> > >>> On Fri, 2012-07-20 at 13:38 +0530, Rajendra Nayak wrote: > >>>> On Friday 20 July 2012 12:55 PM, Shilimkar, Santosh wrote: > >>>>> On Fri, Jul 20, 2012 at 11:34 AM, Rajendra Nayak<rnayak@xxxxxx> wrote: > >>>>>> pwrdm_pre_transition()/pwrdm_post_transition() have always been high latency > >>>>>> operations done within cpuidle to do Powerdomain level book-keeping to know > >>>>>> what state transitions for different Powerdomains have been triggered. > >>>>>> This is also useful to do a restore-on-demand in some cases when we know > >>>>>> the context for the given Powerdomain was lost etc. > >>>>>> > >>>>>> Now that we have definitive entry/exit points (thanks to the Powerdomain > >>>>>> level usecounting) for Powerdomain transitions, these book-keeping functions > >>>>>> can very well be moved from within CPUidle into pwrdm_clkdm_enable()/pwrdm_ > >>>>>> clkdm_disable() functions. > >>>>>> > >>>>>> Also rename _pwrdm_pre/post_transition_cb() to pwrdm_pre/post_transition() > >>>>>> and get rid of the original ones which iterate over all powerdomains. > >>>>>> > >>>>>> Signed-off-by: Rajendra Nayak<rnayak@xxxxxx> > >> > >> This is excellent! Thanks for working on this. > >> > >> However, it needs a rebase against mainline though because I merged a > >> set of optimizations[1] to this code already that only calls pre/post > >> per-pwrdm. > >> > > > > Hi Kevin, > > > > I thought some more on this patch, and I think this way of collecting > > stats and knowing what state transitions the powerdomains been through > > will not work on OMAP3, mainly because of the autodeps. Might work on > > OMAP4 and beyond which do not need any autodeps. > > > > Here why I think so, > > Lets assume a Powerdomain X with a last module Y active, once Y disables > > the last clock (lets assume no hardware controlled clocks for > > simplicity), we clear the last power state register for X. However > > due to autodeps X does not transition to a target state immediately. > > It only does so when the MPU (and IVA) go down, and because > > of the wakeup dependency (autodeps set a sleep and a wakeup dep with > > both MPU and IVA) is also woken up every time MPU or IVA are up. > > So its quite possible that X transitions in and out of sleep multiple > > times before Y decides to re-enable its clocks, which is when we end up > > looking for the last power state entered. > > Lets say X entered OFF 3 times in between Y disabling and re-enabling > > its clocks. Though we end up updating the counter only once (instead of > > 3) we still know and can tell Y that it lost context. > > The problem however arises if for some reason X entered OFF > > twice and happened to stay ON the third time the dependencies were met. > > When Y re-enables its clocks, we end up telling it that it *did not* > > lose context because we see the previous power state was ON. > > Yeah, this is definitely a problem. > > As long as we have autodeps, everything is centralized around CPU > transitions anyways, so it makes sense to keep the accounting > centralized too. > > > I think as long as we have autodeps, the only way on OMAP3 to accurately > > do this is to do it for all dependent domains in CPUIdle :( > > Or, to get rid of autodeps. ;) Whats the reason for having them anyway? Some of the wakedeps make sense (per domain due to hw bugs) but sleepdeps...? -Tero -- 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
