On 11/28/2011 04:37 AM, Benjamin Herrenschmidt wrote: > On Thu, 2011-11-17 at 16:59 +0530, Deepthi Dharwar wrote: >> This patch makes pseries_idle_driver not to be registered when >> power_save=off kernel boot option is specified. The >> boot_option_idle_override variable used here is similar to >> its usage on x86. > > Quick Q. With your changes, the CPU will never get into idle at all > until cpuidle initializes and the driver loads. > > That means not only much later in the boot process, but potentially > never if the distro has the driver as a module and fails to load it, or > similar. > > Can't that be an issue ? Shouldn't we keep at least one of the basic > idle functions as a fallback ? > On an LPAR if cpuidle is disabled, ppc_md.power_save is still set to cpuidle_idle_call by default here. This would result in calling of cpuidle_idle_call repeatedly, only for the call to return -ENODEV. The default idle is never executed. This would be a major design flaw. No fallback idle routine. We propose to fix this by checking the return value of ppc_md.power_save() call from void to int. Right now return value is void, but if we change this to int, this would solve two problems. One being removing the cast to a function pointer in the prev patch and this design flaw stated above. So by checking the return value of ppc_md.power_save(), we can invoke the default idle on failure. But my only concern is about the effects of changing the ppc_md.power_save() to return int on other powerpc architectures. Would it be a good idea to change the return type to int which would help us flag an error and fallback to default idle? > Cheers, > Ben. > > Regards, Deepthi _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/linux-pm
