On Thu, Mar 21, 2013 at 02:52:21PM +0000, Santosh Shilimkar wrote:
[...]
How about taking care of cpu_pm_notifiers() as well with some additional flag for CPU and cluster power state. That can help to reduce and consolidate the code. What you say ?
Do you mean add a flag for different level of idle (idle, suspend, power off) and then use the cpu_pm_enter/cpu_cluster_pm_enter in all the drivers as a common framework ?
I mean only for CPUidle considering C-state already has the information about CPU and cluster power state. For suspend, we by-default run the notifiers so nothing needs to be done there.
You may not even need a framework. Just like we know in a C-state, timer stops, same lines, we can say CPU state is going to be say off and hence cpu_pm_enter() notifier needs to be called. And same way for cluster.
I still haven't given complete thought but thought crossed my mind after looking at your patches.
Right, that could be interesting.
I see may be one issue with this approach: when we enter an idle state with power off, some checking are done before cpu_pm_enter and that could lead to abort the current idle routine.
I see your point.
By moving this to the cpuidle framework, we will invoke always cpu_pm_enter/exit even if the idle enter routine failed.
If we at all decide to go on this path, we can always get around the issues. The key is these notifiers have to be run very close to the low power entry/exit since the saved context for CPU/CPU cluster at wrong points would lead to many issues.
But, IMO, the idea is good.
For example in cpuidle34xx:
static int __omap3_enter_idle(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { struct omap3_idle_statedata *cx = &omap3_idle_data[index];
local_fiq_disable(); if (omap_irq_pending() || need_resched()) goto return_sleep_time;...
if (cx->mpu_state == PWRDM_POWER_OFF) cpu_pm_enter();... }
The same for omap4 and tegra2/3.
With your knowledge of omap, do you think it is possible to move cpu_pm_enter before entering the idle routine ?
I will get back on this topic after some experiments most likely by next week.
Looks like the way to go, we could enhance the notifiers to be able to save/restore specific subsystems with the C-state flags defining which ones.
Notifiers actions should not be disruptive so the only drawback in executing those before entering the idle routine could possibly be a waste of cycles in case the C-state entry fails but certainly something to verify on all platforms using them.
Lorenzo