Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752827Ab3FRHR7 (ORCPT ); Tue, 18 Jun 2013 03:17:59 -0400 Received: from mail-pa0-f45.google.com ([209.85.220.45]:45990 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750873Ab3FRHR6 (ORCPT ); Tue, 18 Jun 2013 03:17:58 -0400 From: Magnus Damm To: linux-kernel@vger.kernel.org Cc: mark.rutland@arm.com, linux-sh@vger.kernel.org, marc.zyngier@arm.com, catalin.marinas@arm.com, horms@verge.net.au, john.stultz@linaro.org, shinya.kuribayashi.px@renesas.com, Magnus Damm , tglx@linutronix.de Date: Tue, 18 Jun 2013 16:17:56 +0900 Message-Id: <20130618071756.22598.51046.sendpatchset@w520> Subject: [PATCH/RFC] clockevents: Ignore C3STOP when CPUIdle is disabled Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4344 Lines: 120 From: Magnus Damm Introduce the function tick_device_may_c3stop() that ignores the C3STOP flag in case CPUIdle is disabled. The C3STOP flag tells the system that a clock event device may be stopped during deep sleep, but if this will happen or not depends on things like if CPUIdle is enabled and if a CPUIdle driver is available. This patch assumes that if CPUIdle is disabled then the sleep mode triggering C3STOP will never be entered. So by ignoring C3STOP when CPUIdle is disabled then it becomes possible to use high resolution timers with only per-cpu local timers - regardless if they have the C3STOP flag set or not. Observed on the r8a73a4 SoC that at this point only uses ARM architected timers for clock event and clock sources. Without this patch high resolution timers are run time disabled on the r8a73a4 SoC - this regardless of CPUIdle is disabled or not. The less short term fix is to add support for more timers on the r8a73a4 SoC, but until CPUIdle support is enabled it must be possible to use high resoultion timers without additional timers. I'd like to hear some feedback and also test this on more systems before merging the code, see the non-SOB below. Not-Yet-Signed-off-by: Magnus Damm --- An earlier ARM arch timer specific version of this patch was posted yesterday as: "[PATCH/RFC] arm: arch_timer: Do not set C3STOP in case CPU_IDLE=n" Many thanks to Mark Rutland for his kind feedback. kernel/time/tick-broadcast.c | 8 ++++---- kernel/time/tick-common.c | 2 +- kernel/time/tick-internal.h | 11 +++++++++++ 3 files changed, 16 insertions(+), 5 deletions(-) --- 0001/kernel/time/tick-broadcast.c +++ work/kernel/time/tick-broadcast.c 2013-06-18 15:36:21.000000000 +0900 @@ -71,7 +71,7 @@ int tick_check_broadcast_device(struct c if ((dev->features & CLOCK_EVT_FEAT_DUMMY) || (tick_broadcast_device.evtdev && tick_broadcast_device.evtdev->rating >= dev->rating) || - (dev->features & CLOCK_EVT_FEAT_C3STOP)) + tick_device_may_c3stop(dev)) return 0; clockevents_exchange_device(tick_broadcast_device.evtdev, dev); @@ -146,7 +146,7 @@ int tick_device_uses_broadcast(struct cl * feature and the cpu is marked in the broadcast mask * then clear the broadcast bit. */ - if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) { + if (!tick_device_may_c3stop(dev)) { int cpu = smp_processor_id(); cpumask_clear_cpu(cpu, tick_broadcast_mask); tick_broadcast_clear_oneshot(cpu); @@ -270,7 +270,7 @@ static void tick_do_broadcast_on_off(uns /* * Is the device not affected by the powerstate ? */ - if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP)) + if (!dev || !tick_device_may_c3stop(dev)) goto out; if (!tick_device_is_functional(dev)) @@ -568,7 +568,7 @@ void tick_broadcast_oneshot_control(unsi td = &per_cpu(tick_cpu_device, cpu); dev = td->evtdev; - if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) + if (!tick_device_may_c3stop(dev)) return; bc = tick_broadcast_device.evtdev; --- 0001/kernel/time/tick-common.c +++ work/kernel/time/tick-common.c 2013-06-18 15:36:29.000000000 +0900 @@ -52,7 +52,7 @@ int tick_is_oneshot_available(void) if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT)) return 0; - if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) + if (!tick_device_may_c3stop(dev)) return 1; return tick_broadcast_oneshot_available(); } --- 0001/kernel/time/tick-internal.h +++ work/kernel/time/tick-internal.h 2013-06-18 15:40:10.000000000 +0900 @@ -141,6 +141,17 @@ static inline int tick_device_is_functio return !(dev->features & CLOCK_EVT_FEAT_DUMMY); } +/* + * Check, if the device has C3STOP behavior and CPU Idle is enabled + */ +static inline bool tick_device_may_c3stop(struct clock_event_device *dev) +{ + /* The C3 sleep mode can only trigger when CPU Idle is enabled, + * so if CPU Idle is disabled then the C3STOP flag can be ignored */ + return (IS_ENABLED(CONFIG_CPU_IDLE) && + (dev->features & CLOCK_EVT_FEAT_C3STOP)); +} + #endif extern void do_timer(unsigned long ticks); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/