| Message ID | 1395744087-8655-1-git-send-email-k.kozlowski@samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Krzysztof, Two comments inline. On 25.03.2014 11:41, Krzysztof Kozlowski wrote: [snip] > diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c > index 48f76bc05da0..0b49b09dd1a9 100644 > --- a/drivers/clocksource/exynos_mct.c > +++ b/drivers/clocksource/exynos_mct.c > @@ -339,7 +339,14 @@ static void exynos4_mct_tick_start(unsigned long cycles, > static int exynos4_tick_set_next_event(unsigned long cycles, > struct clock_event_device *evt) > { > - struct mct_clock_event_device *mevt = this_cpu_ptr(&percpu_mct_tick); > + /* > + * In case of hotplugging non-boot CPU, the set_next_event could be > + * called on CPU0 by ISR before IRQ affinity is set to proper CPU. Hmm, is this a desired behavior? I guess this is a question for Thomas and Daniel. > + * Thus for accessing proper MCT Lx timer, 'per_cpu' for cpumask > + * in event must be used instead of 'this_cpu_ptr'. > + */ > + struct mct_clock_event_device *mevt = &per_cpu(percpu_mct_tick, > + cpumask_first(evt->cpumask)); > > exynos4_mct_tick_start(cycles, mevt); > > @@ -371,23 +378,13 @@ static inline void exynos4_tick_set_mode(enum clock_event_mode mode, > > static int exynos4_mct_tick_clear(struct mct_clock_event_device *mevt) > { > - struct clock_event_device *evt = &mevt->evt; > - > - /* > - * This is for supporting oneshot mode. > - * Mct would generate interrupt periodically > - * without explicit stopping. > - */ > - if (evt->mode != CLOCK_EVT_MODE_PERIODIC) > - exynos4_mct_tick_stop(mevt); > - > /* Clear the MCT tick interrupt */ > if (__raw_readl(reg_base + mevt->base + MCT_L_INT_CSTAT_OFFSET) & 1) { > exynos4_mct_write(0x1, mevt->base + MCT_L_INT_CSTAT_OFFSET); > return 1; > - } else { > - return 0; > } > + > + return 0; Nobody seems to be checking return value of this function (and I don't see what it could be used for anyway), so I guess it could be simply made void. Best regards, Tomasz -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, 2014-03-25 at 12:32 +0100, Tomasz Figa wrote: > Hi Krzysztof, > > Two comments inline. > > On 25.03.2014 11:41, Krzysztof Kozlowski wrote: > > [snip] > > > diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c > > index 48f76bc05da0..0b49b09dd1a9 100644 > > --- a/drivers/clocksource/exynos_mct.c > > +++ b/drivers/clocksource/exynos_mct.c > > @@ -339,7 +339,14 @@ static void exynos4_mct_tick_start(unsigned long cycles, > > static int exynos4_tick_set_next_event(unsigned long cycles, > > struct clock_event_device *evt) > > { > > - struct mct_clock_event_device *mevt = this_cpu_ptr(&percpu_mct_tick); > > + /* > > + * In case of hotplugging non-boot CPU, the set_next_event could be > > + * called on CPU0 by ISR before IRQ affinity is set to proper CPU. > > Hmm, is this a desired behavior? I guess this is a question for Thomas > and Daniel. > > > + * Thus for accessing proper MCT Lx timer, 'per_cpu' for cpumask > > + * in event must be used instead of 'this_cpu_ptr'. > > + */ > > + struct mct_clock_event_device *mevt = &per_cpu(percpu_mct_tick, > > + cpumask_first(evt->cpumask)); > > > > exynos4_mct_tick_start(cycles, mevt); > > > > @@ -371,23 +378,13 @@ static inline void exynos4_tick_set_mode(enum clock_event_mode mode, > > > > static int exynos4_mct_tick_clear(struct mct_clock_event_device *mevt) > > { > > - struct clock_event_device *evt = &mevt->evt; > > - > > - /* > > - * This is for supporting oneshot mode. > > - * Mct would generate interrupt periodically > > - * without explicit stopping. > > - */ > > - if (evt->mode != CLOCK_EVT_MODE_PERIODIC) > > - exynos4_mct_tick_stop(mevt); > > - > > /* Clear the MCT tick interrupt */ > > if (__raw_readl(reg_base + mevt->base + MCT_L_INT_CSTAT_OFFSET) & 1) { > > exynos4_mct_write(0x1, mevt->base + MCT_L_INT_CSTAT_OFFSET); > > return 1; > > - } else { > > - return 0; > > } > > + > > + return 0; > > Nobody seems to be checking return value of this function (and I don't > see what it could be used for anyway), so I guess it could be simply > made void. I'll send a another patch for it. Best regards, Krzysztof -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c index 48f76bc05da0..0b49b09dd1a9 100644 --- a/drivers/clocksource/exynos_mct.c +++ b/drivers/clocksource/exynos_mct.c @@ -339,7 +339,14 @@ static void exynos4_mct_tick_start(unsigned long cycles, static int exynos4_tick_set_next_event(unsigned long cycles, struct clock_event_device *evt) { - struct mct_clock_event_device *mevt = this_cpu_ptr(&percpu_mct_tick); + /* + * In case of hotplugging non-boot CPU, the set_next_event could be + * called on CPU0 by ISR before IRQ affinity is set to proper CPU. + * Thus for accessing proper MCT Lx timer, 'per_cpu' for cpumask + * in event must be used instead of 'this_cpu_ptr'. + */ + struct mct_clock_event_device *mevt = &per_cpu(percpu_mct_tick, + cpumask_first(evt->cpumask)); exynos4_mct_tick_start(cycles, mevt); @@ -371,23 +378,13 @@ static inline void exynos4_tick_set_mode(enum clock_event_mode mode, static int exynos4_mct_tick_clear(struct mct_clock_event_device *mevt) { - struct clock_event_device *evt = &mevt->evt; - - /* - * This is for supporting oneshot mode. - * Mct would generate interrupt periodically - * without explicit stopping. - */ - if (evt->mode != CLOCK_EVT_MODE_PERIODIC) - exynos4_mct_tick_stop(mevt); - /* Clear the MCT tick interrupt */ if (__raw_readl(reg_base + mevt->base + MCT_L_INT_CSTAT_OFFSET) & 1) { exynos4_mct_write(0x1, mevt->base + MCT_L_INT_CSTAT_OFFSET); return 1; - } else { - return 0; } + + return 0; } static irqreturn_t exynos4_mct_tick_isr(int irq, void *dev_id) @@ -395,6 +392,13 @@ static irqreturn_t exynos4_mct_tick_isr(int irq, void *dev_id) struct mct_clock_event_device *mevt = dev_id; struct clock_event_device *evt = &mevt->evt; + /* + * This is for supporting oneshot mode. + * Mct would generate interrupt periodically + * without explicit stopping. + */ + if (evt->mode != CLOCK_EVT_MODE_PERIODIC) + exynos4_mct_tick_stop(mevt); exynos4_mct_tick_clear(mevt); evt->event_handler(evt); @@ -441,7 +445,10 @@ static int exynos4_local_timer_setup(struct clock_event_device *evt) static void exynos4_local_timer_stop(struct clock_event_device *evt) { + struct mct_clock_event_device *mevt = this_cpu_ptr(&percpu_mct_tick); + evt->set_mode(CLOCK_EVT_MODE_UNUSED, evt); + exynos4_mct_tick_clear(mevt); if (mct_int_type == MCT_INT_SPI) free_irq(evt->irq, this_cpu_ptr(&percpu_mct_tick)); else
Fix stall after hotplugging CPU1. The stall was a result of starting the CPU1 local timer not in L1 timer but in L0 (which is used by CPU0). Trigger: $ echo 0 > /sys/bus/cpu/devices/cpu1/online && echo 1 > /sys/bus/cpu/devices/cpu1/online Stall information: [ 530.045259] INFO: rcu_preempt detected stalls on CPUs/tasks: [ 530.045618] 1: (6 GPs behind) idle=6d0/0/0 softirq=369/369 [ 530.050987] (detected by 0, t=6589 jiffies, g=33, c=32, q=0) [ 530.056721] Task dump for CPU 1: [ 530.059928] swapper/1 R running 0 0 1 0x00001000 [ 530.066377] [<c0524e14>] (__schedule+0x414/0x9b4) from [<c00b6610>] (rcu_idle_enter+0x18/0x38) [ 530.074955] [<c00b6610>] (rcu_idle_enter+0x18/0x38) from [<c0079a18>] (cpu_startup_entry+0x60/0x3bc) [ 530.084069] [<c0079a18>] (cpu_startup_entry+0x60/0x3bc) from [<c0517d34>] (secondary_start_kernel+0x164/0x1a0) [ 530.094029] [<c0517d34>] (secondary_start_kernel+0x164/0x1a0) from [<40517244>] (0x40517244) The timers for CPU1 were missed: [ 591.668436] cpu: 1 [ 591.670430] clock 0: [ 591.672691] .base: c0ab7750 [ 591.676160] .index: 0 [ 591.679025] .resolution: 1 nsecs [ 591.682404] .get_time: ktime_get [ 591.685970] .offset: 0 nsecs [ 591.689349] active timers: [ 591.692045] #0: <dfb51f40>, hrtimer_wakeup, S:01 [ 591.696759] # expires at 454687834257-454687884257 nsecs [in -136770537232 to -136770487232 nsecs] And the event_handler for next event was wrong: [ 591.917120] Tick Device: mode: 1 [ 591.920676] Per CPU device: 0 [ 591.923621] Clock Event Device: mct_tick0 [ 591.927623] max_delta_ns: 178956969027 [ 591.931613] min_delta_ns: 1249 [ 591.934913] mult: 51539608 [ 591.938557] shift: 32 [ 591.941681] mode: 3 [ 591.944724] next_event: 595025000000 nsecs [ 591.949227] set_next_event: exynos4_tick_set_next_event [ 591.954522] set_mode: exynos4_tick_set_mode [ 591.959296] event_handler: hrtimer_interrupt [ 591.963730] retries: 0 [ 591.966761] [ 591.968245] Tick Device: mode: 0 [ 591.971801] Per CPU device: 1 [ 591.974746] Clock Event Device: mct_tick1 [ 591.978750] max_delta_ns: 178956969027 [ 591.982739] min_delta_ns: 1249 [ 591.986037] mult: 51539608 [ 591.989681] shift: 32 [ 591.992806] mode: 3 [ 591.995848] next_event: 453685000000 nsecs [ 592.000353] set_next_event: exynos4_tick_set_next_event [ 592.005648] set_mode: exynos4_tick_set_mode [ 592.010421] event_handler: tick_handle_periodic [ 592.015115] retries: 0 [ 592.018145] After turning off the CPU1, the MCT L1 local timer was disabled but the interrupt was not cleared. Turning on the CPU1 enabled the IRQ with setup_irq() but, before setting affinity to CPU1, the pending L1 timer interrupt was processed by CPU0 in exynos4_mct_tick_isr(). The ISR then called event handler which set up the next timer event for current CPU (CPU0). Therefore the MCT L1 timer wasn't actually started. Fix the stall by: 1. Setting next timer event not on current CPU but on the CPU indicated by cpumask in 'clock_event_device'. 2. Clearing the timer interrupt upon stopping the local timer. The patch also moves around the call to exynos4_mct_tick_stop() but this is done only for the code readability as it is not essential for the fix. Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com> --- drivers/clocksource/exynos_mct.c | 33 ++++++++++++++++++++------------- 1 file changed, 20 insertions(+), 13 deletions(-)