On 11/29/2011 12:14 PM, Deepthi Dharwar wrote: > On 11/29/2011 02:09 AM, Benjamin Herrenschmidt wrote: > >> On Mon, 2011-11-28 at 16:33 +0530, Deepthi Dharwar wrote: >> >>> 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. kernel/idle.c: ppc_md.power_save = NULL; >>> >>> 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? >> >> I would have preferred an approach where the cpuidle module sets >> ppc_md.power_save when loaded and restores it when unloaded ... but that >> would have to go into the cpuidle core as a powerpc specific tweak and >> might not be generally well received. >> >> So go for it, add the return value, but you'll have to update all the >> idle functions (grep for power_save in arch/powerpc to find them). >> > > > Thanks Ben. Yes, I will update all the idle functions under powerpc. > I will re-work these patches with the discussed changes. > > Regards, > Deepthi > > _______________________________________________ > linux-pm mailing list > linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx > https://lists.linuxfoundation.org/mailman/listinfo/linux-pm > > Hi Ben, I was trying to add a return value for power_save for all arch/powepc idle functions but a few of them directly call *.S routines, as they are asm. What would be a good way to change the return value for asm routines ? Do we make a change in asm only, put the return value in r3 or write a wrapper function which would call these asm routines and return an int ? Regards, Deepthi _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/linux-pm
