From 82a5619410d4c4df65c04272db198eca5a867c18 Mon Sep 17 00:00:00 2001 From: Lorenzo Pieralisi Date: Tue, 8 Apr 2014 10:04:32 +0100 Subject: [PATCH 1/5] clocksource: arch_arm_timer: Fix age-old arch timer C3STOP detection issue ARM arch timers are tightly coupled with the CPU logic and lose context on platform implementing HW power management when cores are powered down at run-time. Marking the arch timers as C3STOP regardless of power management capabilities causes issues on platforms with no power management, since in that case the arch timers cannot possibly enter states where the timer loses context at runtime and therefore can always be used as a high resolution clockevent device. In order to fix the C3STOP issue in a way compliant with how real HW works, this patch adds a boolean property to the arch timer bindings to define if the arch timer is managed by an always-on power domain. This power domain is present on all ARM platforms to date, and manages HW that must not be turned off, whatever the state of other HW components (eg power controller). On platforms with no power management capabilities, it is the only power domain present, which encompasses and manages power supply for all HW components in the system. If the timer is powered by the always-on power domain, the always-on property must be present in the bindings which means that the timer cannot be shutdown at runtime, so it is not a C3STOP clockevent device. If the timer binding does not contain the always-on property, the timer is assumed to be power-gateable, hence it must be defined as a C3STOP clockevent device. Cc: Daniel Lezcano Cc: Magnus Damm Cc: Marc Carino Cc: Mark Rutland Acked-by: Marc Zyngier Acked-by: Rob Herring Signed-off-by: Lorenzo Pieralisi Signed-off-by: Daniel Lezcano --- Documentation/devicetree/bindings/arm/arch_timer.txt | 3 +++ drivers/clocksource/arm_arch_timer.c | 6 +++++- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/Documentation/devicetree/bindings/arm/arch_timer.txt b/Documentation/devicetree/bindings/arm/arch_timer.txt index 06fc7602593a9..37b2cafa4e527 100644 --- a/Documentation/devicetree/bindings/arm/arch_timer.txt +++ b/Documentation/devicetree/bindings/arm/arch_timer.txt @@ -19,6 +19,9 @@ to deliver its interrupts via SPIs. - clock-frequency : The frequency of the main counter, in Hz. Optional. +- always-on : a boolean property. If present, the timer is powered through an + always-on power domain, therefore it never loses context. + Example: timer { diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c index 57e823c44d2ad..5163ec13429d1 100644 --- a/drivers/clocksource/arm_arch_timer.c +++ b/drivers/clocksource/arm_arch_timer.c @@ -66,6 +66,7 @@ static int arch_timer_ppi[MAX_TIMER_PPI]; static struct clock_event_device __percpu *arch_timer_evt; static bool arch_timer_use_virtual = true; +static bool arch_timer_c3stop; static bool arch_timer_mem_use_virtual; /* @@ -263,7 +264,8 @@ static void __arch_timer_setup(unsigned type, clk->features = CLOCK_EVT_FEAT_ONESHOT; if (type == ARCH_CP15_TIMER) { - clk->features |= CLOCK_EVT_FEAT_C3STOP; + if (arch_timer_c3stop) + clk->features |= CLOCK_EVT_FEAT_C3STOP; clk->name = "arch_sys_timer"; clk->rating = 450; clk->cpumask = cpumask_of(smp_processor_id()); @@ -665,6 +667,8 @@ static void __init arch_timer_init(struct device_node *np) } } + arch_timer_c3stop = !of_property_read_bool(np, "always-on"); + arch_timer_register(); arch_timer_common_init(); } From 9afa27ce9414c92e271b0d7eec937bd9f5565da5 Mon Sep 17 00:00:00 2001 From: Alexander Shiyan Date: Sat, 26 Apr 2014 09:32:16 +0400 Subject: [PATCH 2/5] clocksource: nspire: Fix compiler warning CC drivers/clocksource/zevio-timer.o drivers/clocksource/zevio-timer.c:215:1: warning: comparison of distinct pointer types lacks a cast [enabled by default] Signed-off-by: Alexander Shiyan Signed-off-by: Daniel Lezcano --- drivers/clocksource/zevio-timer.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/clocksource/zevio-timer.c b/drivers/clocksource/zevio-timer.c index ca81809d159d5..7ce442148c3f5 100644 --- a/drivers/clocksource/zevio-timer.c +++ b/drivers/clocksource/zevio-timer.c @@ -212,4 +212,9 @@ static int __init zevio_timer_add(struct device_node *node) return ret; } -CLOCKSOURCE_OF_DECLARE(zevio_timer, "lsi,zevio-timer", zevio_timer_add); +static void __init zevio_timer_init(struct device_node *node) +{ + BUG_ON(zevio_timer_add(node)); +} + +CLOCKSOURCE_OF_DECLARE(zevio_timer, "lsi,zevio-timer", zevio_timer_init); From 6c6c0d5a1c949d2e084706f9e5fb1fccc175b265 Mon Sep 17 00:00:00 2001 From: Stuart Hayes Date: Tue, 29 Apr 2014 17:55:02 -0500 Subject: [PATCH 3/5] hrtimer: Prevent all reprogramming if hang detected If the last hrtimer interrupt detected a hang it sets hang_detected=1 and programs the clock event device with a delay to let the system make progress. If hang_detected == 1, we prevent reprogramming of the clock event device in hrtimer_reprogram() but not in hrtimer_force_reprogram(). This can lead to the following situation: hrtimer_interrupt() hang_detected = 1; program ce device to Xms from now (hang delay) We have two timers pending: T1 expires 50ms from now T2 expires 5s from now Now T1 gets canceled, which causes hrtimer_force_reprogram() to be invoked, which in turn programs the clock event device to T2 (5 seconds from now). Any hrtimer_start after that will not reprogram the hardware due to hang_detected still being set. So we effectivly block all timers until the T2 event fires and cleans up the hang situation. Add a check for hang_detected to hrtimer_force_reprogram() which prevents the reprogramming of the hang delay in the hardware timer. The subsequent hrtimer_interrupt will resolve all outstanding issues. [ tglx: Rewrote subject and changelog and fixed up the comment in hrtimer_force_reprogram() ] Signed-off-by: Stuart Hayes Link: http://lkml.kernel.org/r/53602DC6.2060101@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Thomas Gleixner --- kernel/hrtimer.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index d55092ceee297..e3724fdac2da2 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -569,6 +569,23 @@ hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal) cpu_base->expires_next.tv64 = expires_next.tv64; + /* + * If a hang was detected in the last timer interrupt then we + * leave the hang delay active in the hardware. We want the + * system to make progress. That also prevents the following + * scenario: + * T1 expires 50ms from now + * T2 expires 5s from now + * + * T1 is removed, so this code is called and would reprogram + * the hardware to 5s from now. Any hrtimer_start after that + * will not reprogram the hardware due to hang_detected being + * set. So we'd effectivly block all timers until the T2 event + * fires. + */ + if (cpu_base->hang_detected) + return; + if (cpu_base->expires_next.tv64 != KTIME_MAX) tick_program_event(cpu_base->expires_next, 1); } From 012a45e3f4af68e86d85cce060c6c2fed56498b2 Mon Sep 17 00:00:00 2001 From: Leon Ma Date: Wed, 30 Apr 2014 16:43:10 +0800 Subject: [PATCH 4/5] hrtimer: Prevent remote enqueue of leftmost timers If a cpu is idle and starts an hrtimer which is not pinned on that same cpu, the nohz code might target the timer to a different cpu. In the case that we switch the cpu base of the timer we already have a sanity check in place, which determines whether the timer is earlier than the current leftmost timer on the target cpu. In that case we enqueue the timer on the current cpu because we cannot reprogram the clock event device on the target. If the timers base is already the target CPU we do not have this sanity check in place so we enqueue the timer as the leftmost timer in the target cpus rb tree, but we cannot reprogram the clock event device on the target cpu. So the timer expires late and subsequently prevents the reprogramming of the target cpu clock event device until the previously programmed event fires or a timer with an earlier expiry time gets enqueued on the target cpu itself. Add the same target check as we have for the switch base case and start the timer on the current cpu if it would become the leftmost timer on the target. [ tglx: Rewrote subject and changelog ] Signed-off-by: Leon Ma Link: http://lkml.kernel.org/r/1398847391-5994-1-git-send-email-xindong.ma@intel.com Cc: stable@vger.kernel.org Signed-off-by: Thomas Gleixner --- kernel/hrtimer.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index e3724fdac2da2..6b715c0af1b11 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -234,6 +234,11 @@ switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base, goto again; } timer->base = new_base; + } else { + if (cpu != this_cpu && hrtimer_check_target(timer, new_base)) { + cpu = this_cpu; + goto again; + } } return new_base; } From 98a01e779f3c66b0b11cd7e64d531c0e41c95762 Mon Sep 17 00:00:00 2001 From: Jiri Bohac Date: Fri, 18 Apr 2014 17:23:11 +0200 Subject: [PATCH 5/5] timer: Prevent overflow in apply_slack On architectures with sizeof(int) < sizeof (long), the computation of mask inside apply_slack() can be undefined if the computed bit is > 32. E.g. with: expires = 0xffffe6f5 and slack = 25, we get: expires_limit = 0x20000000e bit = 33 mask = (1 << 33) - 1 /* undefined */ On x86, mask becomes 1 and and the slack is not applied properly. On s390, mask is -1, expires is set to 0 and the timer fires immediately. Use 1UL << bit to solve that issue. Suggested-by: Deborah Townsend Signed-off-by: Jiri Bohac Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20140418152310.GA13654@midget.suse.cz Signed-off-by: Thomas Gleixner --- kernel/timer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/timer.c b/kernel/timer.c index 87bd529879c23..3bb01a323b2a3 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -838,7 +838,7 @@ unsigned long apply_slack(struct timer_list *timer, unsigned long expires) bit = find_last_bit(&mask, BITS_PER_LONG); - mask = (1 << bit) - 1; + mask = (1UL << bit) - 1; expires_limit = expires_limit & ~(mask);