On 06/13/2012 02:44 PM, Jean Pihet wrote: > Hi Daniel, > > On Fri, Jun 8, 2012 at 11:34 PM, Daniel Lezcano > <daniel.lezcano@xxxxxxxxxx> wrote: >> On 06/08/2012 07:33 PM, Deepthi Dharwar wrote: >>> Hi Daniel, >> >> Hi Deepthi, >> >>> On 06/08/2012 09:32 PM, Daniel Lezcano wrote: >>> >>>> We have the state index passed as parameter to the 'enter' function. >>>> Most of the drivers assign their 'enter' functions several times in >>>> the cpuidle_state structure, as we have the index, we can delegate >>>> to the driver to handle their own callback array. >>>> >>>> That will have the benefit of removing multiple lines of code in the >>>> different drivers. >>>> >>>> In order to smoothly modify the driver, the 'enter' function are in >>>> the driver structure and in the cpuidle state structure. That will >>>> let the time to modify the different drivers one by one. >>>> So the 'cpuidle_enter' function checks if the 'enter' callback is >>>> assigned in the driver structure and use it, otherwise it invokes >>>> the 'enter' assigned to the cpuidle_state. >>> >>> >>> Currently, the backend driver initializes >>> all the cpuidle states supported on the platform, >>> and each state can have its own enter routine >>> which can be unique This is a clean approach. >> >> Yes, I perfectly understood the purpose of this field but as clean it is >> it does not make sense as it is not used in this way. If it is supposed >> to be done in the way you are describing here, we should have the same >> number of states and enter functions. Here it is how it is used: >> >> -------------------------------------------------- >> | Arch | nr states | nr enter function | >> -------------------------------------------------- >> | x86 (nehalem) | 3 | 1 | >> -------------------------------------------------- >> | x86 (snb) | 4 | 1 | >> -------------------------------------------------- >> | x86 (atom) | 4 | 1 | >> -------------------------------------------------- >> | ARM tegra | 1 | 1 | >> -------------------------------------------------- >> | ARM omap3 | 7 | 2 | >> -------------------------------------------------- >> | ARM omap4 | 3 | 1 | >> -------------------------------------------------- >> | ARM ux500 | 2 | 1 | >> -------------------------------------------------- >> | ARM shmobile | 1 | 1 | >> -------------------------------------------------- >> | ARM davinci | 2 | 1 | >> -------------------------------------------------- >> | ARM at91 | 2 | 1 | >> -------------------------------------------------- >> | ARM s3c64xx | 1 | 1 | >> -------------------------------------------------- >> | ARM exynos | 2 | 1 | >> -------------------------------------------------- >> | ARM kirkwood | 2 | 1 | >> -------------------------------------------------- >> | SH | 3 | 1 | >> -------------------------------------------------- >> | PPC | 2 | 2 | >> -------------------------------------------------- >> | | | | >> | TOTAL | 39 | 17 | >> | | | | >> -------------------------------------------------- >> >> >> As you can see most of the enter functions are only used as one. >> The Omap3 cpuidle driver enter function for C2 calls the enter function >> of C1. Other arch, already use a table of callbacks or the index. > There is a plan to remove the extra enter function as part of an > optimization, cf. [1]. The fix is planned to reach the 3.6 mainline > kernel via Kevin's tree [2]. > > [1] http://marc.info/?l=linux-omap&m=133856365818099&w=2 > [2] http://git.kernel.org/?p=linux/kernel/git/khilman/linux-omap-pm.git;a=shortlog;h=refs/heads/for_3.6/pm/performance > > The result is that there will be only one enter function for OMAP3. Another argument in favor of moving this field to the driver structure. Thanks Jean for the information. -- Daniel -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/linux-pm
