Re: [v4 PATCH 1/5]: cpuidle: Cleanup drivers/cpuidle/cpuidle.c

* Peter Zijlstra [off-list ref] [2009-09-02 07:42:24]:

On Tue, 2009-09-01 at 17:08 +0530, Arun R Bharadwaj wrote:

quoted

* Arun R Bharadwaj [off-list ref] [2009-09-01 17:07:04]:

Cleanup drivers/cpuidle/cpuidle.c

Cpuidle maintains a pm_idle_old void pointer because, currently in x86
there is no clean way of registering and unregistering a idle function.

Right, and instead of fixing that, they build this cpuidle crap on top,
instead of replacing the current crap with it.

quoted

So remove pm_idle_old and leave the responsibility of maintaining the
list of registered idle loops to the architecture specific code. If the
architecture registers cpuidle_idle_call as its idle loop, only then
this loop is called.

OK, that's a start I guess. Best would be to replace all of pm_idle with
cpuidle, which is what should have been done from the very start.

If cpuidle cannot fully replace the pm_idle functionality, then it needs
to fix that. But having two layers of idle functions is just silly.

Looking at patch 2 and 3, you're making the same mistake on power, after
those patches there are multiple ways of registering idle functions, one
through some native interface and one through cpuidle, this strikes me
as undesirable.

If cpuidle is a good idle function manager, then it should be good
enough to be the sole one, if its not, then why bother with it at all.

Okay, I'm giving this approach a shot now. i.e. trying to make cpuidle
as _the_ sole idle function manager. This would mean doing away with
pm_idle and ppc_md.power_save. And, cpuidle_idle_call() which is the
main idle loop of cpuidle, present in drivers/cpuidle/cpuidle.c will
have to be called from arch specific code of cpu_idle()

Also this would mean enabling cpuidle for all platforms, even if the
platform doesn't have multiple idle states. So suppose a platform doesnt
have multiple states, it wouldn't want the bloated code of cpuidle
governors, and would want just a simple cpuidle loop.

--arun