From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752641AbaBYGf1 (ORCPT ); Tue, 25 Feb 2014 01:35:27 -0500 Received: from mail-we0-f174.google.com ([74.125.82.174]:40184 "EHLO mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752539AbaBYGf0 (ORCPT ); Tue, 25 Feb 2014 01:35:26 -0500 Message-ID: <530C39AE.2050905@linaro.org> Date: Tue, 25 Feb 2014 07:35:26 +0100 From: Daniel Lezcano User-Agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Preeti U Murthy CC: mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de, rjw@rjwysocki.net, nicolas.pitre@linaro.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V2 1/5] idle/cpuidle: Split cpuidle_idle_call main function into smaller functions References: <1393250151-6982-1-git-send-email-daniel.lezcano@linaro.org> <530C126B.4060105@linux.vnet.ibm.com> In-Reply-To: <530C126B.4060105@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/25/2014 04:47 AM, Preeti U Murthy wrote: > Hi Daniel, > > On 02/24/2014 07:25 PM, Daniel Lezcano wrote: >> --- >> drivers/cpuidle/cpuidle.c | 114 ++++++++++++++++++++++++++++++++++------------ >> include/linux/cpuidle.h | 19 +++++++ >> 2 files changed, 105 insertions(+), 28 deletions(-) >> >> Index: cpuidle-next/drivers/cpuidle/cpuidle.c >> =================================================================== >> --- cpuidle-next.orig/drivers/cpuidle/cpuidle.c >> +++ cpuidle-next/drivers/cpuidle/cpuidle.c >> @@ -65,6 +65,26 @@ int cpuidle_play_dead(void) >> } >> >> /** >> + * cpuidle_enabled - check if the cpuidle framework is ready >> + * @dev: cpuidle device for this cpu >> + * @drv: cpuidle driver for this cpu >> + * >> + * Return 0 on success, otherwise: >> + * -NODEV : the cpuidle framework is not available >> + * -EBUSY : the cpuidle framework is not initialized >> + */ >> +int cpuidle_enabled(struct cpuidle_driver *drv, struct cpuidle_device *dev) >> +{ >> + if (off || !initialized) >> + return -ENODEV; >> + >> + if (!drv || !dev || !dev->enabled) >> + return -EBUSY; >> + >> + return 0; >> +} >> + >> +/** >> * cpuidle_enter_state - enter the state and update stats >> * @dev: cpuidle device for this cpu >> * @drv: cpuidle driver for this cpu >> @@ -108,6 +128,63 @@ int cpuidle_enter_state(struct cpuidle_d >> } >> >> /** >> + * cpuidle_select - ask the cpuidle framework to choose an idle state >> + * >> + * @drv: the cpuidle driver >> + * @dev: the cpuidle device >> + * >> + * Returns the index of the idle state. >> + */ >> +int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) >> +{ >> + return cpuidle_curr_governor->select(drv, dev); >> +} >> + >> +/** >> + * cpuidle_enter - enter into the specified idle state >> + * >> + * @drv: the cpuidle driver tied with the cpu >> + * @dev: the cpuidle device >> + * @index: the index in the idle state table >> + * >> + * Returns the index in the idle state, < 0 in case of error. >> + * The error code depends on the backend driver >> + */ >> +int cpuidle_enter(struct cpuidle_driver *drv, struct cpuidle_device *dev, >> + int index) >> +{ >> + int entered_state; >> + bool broadcast = !!(drv->states[index].flags & CPUIDLE_FLAG_TIMER_STOP); >> + >> + if (broadcast) >> + clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu); >> + >> + if (cpuidle_state_is_coupled(dev, drv, index)) >> + entered_state = cpuidle_enter_state_coupled(dev, drv, index); >> + else >> + entered_state = cpuidle_enter_state(dev, drv, index); >> + >> + if (broadcast) >> + clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu); >> + >> + return entered_state; >> +} >> + >> +/** >> + * cpuidle_reflect - tell the underlying governor what was the state >> + * we were in >> + * >> + * @dev : the cpuidle device >> + * @index: the index in the idle state table >> + * >> + */ >> +void cpuidle_reflect(struct cpuidle_device *dev, int index) >> +{ >> + if (cpuidle_curr_governor->reflect) >> + cpuidle_curr_governor->reflect(dev, index); >> +} >> + >> +/** >> * cpuidle_idle_call - the main idle loop >> * >> * NOTE: no locks or semaphores should be used here >> @@ -116,51 +193,32 @@ int cpuidle_enter_state(struct cpuidle_d >> int cpuidle_idle_call(void) >> { >> struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices); >> - struct cpuidle_driver *drv; >> + struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); >> int next_state, entered_state; >> - bool broadcast; >> >> - if (off || !initialized) >> - return -ENODEV; >> - >> - /* check if the device is ready */ >> - if (!dev || !dev->enabled) >> - return -EBUSY; >> - >> - drv = cpuidle_get_cpu_driver(dev); >> + next_state = cpuidle_enabled(drv, dev); > > Accepting the return of cpuidle_enabled() into a parameter named > "next_state" looks misleading. You are not returning any idle state. You > could use ret/enabled to accept the return value here perhaps? Yes, it was to save an extra variable. I can replace it by a 'ret'. >> + if (next_state < 0) >> + return next_state; >> >> /* ask the governor for the next state */ >> - next_state = cpuidle_curr_governor->select(drv, dev); >> + next_state = cpuidle_select(drv, dev); >> + >> if (need_resched()) { >> dev->last_residency = 0; >> /* give the governor an opportunity to reflect on the outcome */ >> - if (cpuidle_curr_governor->reflect) >> - cpuidle_curr_governor->reflect(dev, next_state); >> + cpuidle_reflect(dev, next_state); >> local_irq_enable(); >> return 0; >> } >> >> trace_cpu_idle_rcuidle(next_state, dev->cpu); >> >> - broadcast = !!(drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP); >> - >> - if (broadcast) >> - clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu); >> - >> - if (cpuidle_state_is_coupled(dev, drv, next_state)) >> - entered_state = cpuidle_enter_state_coupled(dev, drv, >> - next_state); >> - else >> - entered_state = cpuidle_enter_state(dev, drv, next_state); >> - >> - if (broadcast) >> - clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu); >> + entered_state = cpuidle_enter(drv, dev, next_state); > > Shouldn't the return value be checked here, considering you are > expecting the driver to return an error code. Another reason I mention > this is that since you would have done BROADCAST_ENTRY and if this call > to the broadcast framework succeeds, you will have to do a > BROADCAST_EXIT irrespective of if the driver could put the CPU to that > idle state or not. So even if cpuidle_enter() fails, you will need to do > a clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu), > although you will have to skip over cpuidle_reflect(). > > So are there drivers which can return an error code when we call into > the enter function of the idle states? Except for the acpi noodle plate driver, no backend driver is returning an error. > If not, you can probably avoid > checking the error code return value of cpuidle_enter() altogether and > make it simpler. Its not being checked in the current code too. Yeah, that is the point. I don't want to mix the changes with this patchset. I agree, the code must be fixed but I prefer to do that in a separate patch. Thanks for the review -- Daniel > > Thanks > > Regards > Preeti U Murthy >> >> trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu); >> >> /* give the governor an opportunity to reflect on the outcome */ >> - if (cpuidle_curr_governor->reflect) >> - cpuidle_curr_governor->reflect(dev, entered_state); >> + cpuidle_reflect(dev, entered_state); >> >> return 0; >> } > -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog