From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cam-admin0.cambridge.arm.com (cam-admin0.cambridge.arm.com [217.140.96.50]) by lists.ozlabs.org (Postfix) with ESMTP id 5E9801A01C9 for ; Mon, 8 Dec 2014 23:12:21 +1100 (AEDT) Date: Mon, 8 Dec 2014 12:11:10 +0000 From: Mark Rutland To: Preeti U Murthy Subject: Re: [PATCH V2] tick-broadcast: Register for hrtimer based broadcast as the fallback broadcast mode Message-ID: <20141208121110.GC21680@leverpostej> References: <20141208065513.3075.48721.stgit@preeti.in.ibm.com> <20141208104828.GA21680@leverpostej> <5485936F.20901@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <5485936F.20901@linux.vnet.ibm.com> Cc: Lorenzo Pieralisi , "peterz@infradead.org" , "fweisbec@gmail.com" , "rafael.j.wysocki@intel.com" , Will Deacon , "linux-kernel@vger.kernel.org" , "jingchang.lu@freescale.com" , "tglx@linutronix.de" , "shawn.guo@linaro.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-arm-kernel@lists.infradead.org" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, Dec 08, 2014 at 12:02:55PM +0000, Preeti U Murthy wrote: > On 12/08/2014 04:18 PM, Mark Rutland wrote: > > Hi Preeti, > > > > On Mon, Dec 08, 2014 at 06:55:43AM +0000, Preeti U Murthy wrote: > >> Commit 5d1638acb9f6 ('tick: Introduce hrtimer based broadcast') added a > >> hrtimer based broadcast mode for those platforms in which local timers stop > >> when CPUs enter deep idle states. The commit expected the platforms to > >> register for this mode explicitly when they lacked a better external device > >> to wake up CPUs in deep idle. Given that more platforms are beginning to use > >> this mode, we can avoid the call to set it up on every platform that requires > >> it, by registering for the hrtimer based broadcast mode in the core code if > >> no better broadcast device is available. > >> > >> This commit also helps detect cases where the platform fails to register for > >> a broadcast device but invokes the help of one when entering deep idle states. > >> Currently we do not handle this situation at all and call the broadcast clock > >> device without checking for its existence. This patch will handle such buggy > >> cases properly. > >> > >> Signed-off-by: Preeti U Murthy > > > > I've just given this a go on an arm64 platform (Juno) without any > > system-wide clock_event_devices registered, and everything works well > > with CPUs entering and exiting idle states where the cpu-local timers > > lose state. So: > > > > Tested-by: Mark Rutland > > Thanks! > > > > > One minor thing I noticed when testing was that > > /sys/devices/system/clockevents/broadcast/name contained "(null)", > > because we never set the name field on the clock_event_device. It's > > always been that way, but now might be a good time to change that to > > something like "broadcast_hrtimer". > > You mean /sys/devices/system/clockevents/broadcast/current_device right? Whoops, yes I did. > > [...] > > > >> diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h > >> index 2e4cb67..91754b0 100644 > >> --- a/include/linux/clockchips.h > >> +++ b/include/linux/clockchips.h > >> @@ -187,11 +187,11 @@ extern int tick_receive_broadcast(void); > >> #endif > >> > >> #if defined(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST) && defined(CONFIG_TICK_ONESHOT) > >> -extern void tick_setup_hrtimer_broadcast(void); > >> +extern int __init tick_setup_hrtimer_broadcast(void); > >> extern int tick_check_broadcast_expired(void); > >> #else > >> static inline int tick_check_broadcast_expired(void) { return 0; } > >> -static inline void tick_setup_hrtimer_broadcast(void) {}; > >> +static inline int __init tick_setup_hrtimer_broadcast(void) { return 0; } > >> #endif > >> > >> #ifdef CONFIG_GENERIC_CLOCKEVENTS > >> @@ -207,7 +207,7 @@ static inline void clockevents_resume(void) {} > >> > >> static inline int clockevents_notify(unsigned long reason, void *arg) { return 0; } > >> static inline int tick_check_broadcast_expired(void) { return 0; } > >> -static inline void tick_setup_hrtimer_broadcast(void) {}; > >> +static inline int __init tick_setup_hrtimer_broadcast(void) { return 0; } > > > > With the initcall moved to the driver we have no external users of > > tick_setup_hrtimer_broadcast, so I think we can remove the prototype > > entirely from clockchips.h... > > > >> #endif > >> > >> diff --git a/kernel/time/tick-broadcast-hrtimer.c b/kernel/time/tick-broadcast-hrtimer.c > >> index eb682d5..5c35995 100644 > >> --- a/kernel/time/tick-broadcast-hrtimer.c > >> +++ b/kernel/time/tick-broadcast-hrtimer.c > >> @@ -98,9 +98,11 @@ static enum hrtimer_restart bc_handler(struct hrtimer *t) > >> return HRTIMER_RESTART; > >> } > >> > >> -void tick_setup_hrtimer_broadcast(void) > >> +int __init tick_setup_hrtimer_broadcast(void) > > > > ...and make it static here. > > Yep will do. Sorry I overlooked this. > > > > >> { > >> hrtimer_init(&bctimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); > >> bctimer.function = bc_handler; > >> clockevents_register_device(&ce_broadcast_hrtimer); > >> + return 0; > >> } > >> +early_initcall(tick_setup_hrtimer_broadcast); > > > > Otherwise this looks good to me, thanks for putting this together! > > Thanks a lot for the review! Will send out the patch with the above > corrections. Cheers! Thanks, Mark.