kernel/time/tick-broadcast.c

   1 /*
   2  * linux/kernel/time/tick-broadcast.c
   3  *
   4  * This file contains functions which emulate a local clock-event
   5  * device via a broadcast event source.
   6  *
   7  * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
   8  * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
   9  * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
  10  *
  11  * This code is licenced under the GPL version 2. For details see
  12  * kernel-base/COPYING.
  13  */
  14 #include <linux/cpu.h>
  15 #include <linux/err.h>
  16 #include <linux/hrtimer.h>
  17 #include <linux/irq.h>
  18 #include <linux/percpu.h>
  19 #include <linux/profile.h>
  20 #include <linux/sched.h>
  21 #include <linux/tick.h>
  22
  23 #include "tick-internal.h"
  24
  25 /*
  26  * Broadcast support for broken x86 hardware, where the local apic
  27  * timer stops in C3 state.
  28  */
  29
  30 struct tick_device tick_broadcast_device;
  31 static cpumask_t tick_broadcast_mask;
  32 DEFINE_SPINLOCK(tick_broadcast_lock);
  33
  34 /*
  35  * Start the device in periodic mode
  36  */
  37 static void tick_broadcast_start_periodic(struct clock_event_device *bc)
  38 {
  39         if (bc && bc->mode == CLOCK_EVT_MODE_SHUTDOWN)
  40                 tick_setup_periodic(bc, 1);
  41 }
  42
  43 /*
  44  * Check, if the device can be utilized as broadcast device:
  45  */
  46 int tick_check_broadcast_device(struct clock_event_device *dev)
  47 {
  48         if (tick_broadcast_device.evtdev ||
  49             (dev->features & CLOCK_EVT_FEAT_C3STOP))
  50                 return 0;
  51
  52         clockevents_exchange_device(NULL, dev);
  53         tick_broadcast_device.evtdev = dev;
  54         if (!cpus_empty(tick_broadcast_mask))
  55                 tick_broadcast_start_periodic(dev);
  56         return 1;
  57 }
  58
  59 /*
  60  * Check, if the device is the broadcast device
  61  */
  62 int tick_is_broadcast_device(struct clock_event_device *dev)
  63 {
  64         return (dev && tick_broadcast_device.evtdev == dev);
  65 }
  66
  67 /*
  68  * Check, if the device is disfunctional and a place holder, which
  69  * needs to be handled by the broadcast device.
  70  */
  71 int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
  72 {
  73         unsigned long flags;
  74         int ret = 0;
  75
  76         spin_lock_irqsave(&tick_broadcast_lock, flags);
  77
  78         /*
  79          * Devices might be registered with both periodic and oneshot
  80          * mode disabled. This signals, that the device needs to be
  81          * operated from the broadcast device and is a placeholder for
  82          * the cpu local device.
  83          */
  84         if (!tick_device_is_functional(dev)) {
  85                 dev->event_handler = tick_handle_periodic;
  86                 cpu_set(cpu, tick_broadcast_mask);
  87                 tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
  88                 ret = 1;
  89         }
  90
  91         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
  92         return ret;
  93 }
  94
  95 /*
  96  * Broadcast the event to the cpus, which are set in the mask
  97  */
  98 int tick_do_broadcast(cpumask_t mask)
  99 {
 100         int ret = 0, cpu = smp_processor_id();
 101         struct tick_device *td;
 102
 103         /*
 104          * Check, if the current cpu is in the mask
 105          */
 106         if (cpu_isset(cpu, mask)) {
 107                 cpu_clear(cpu, mask);
 108                 td = &per_cpu(tick_cpu_device, cpu);
 109                 td->evtdev->event_handler(td->evtdev);
 110                 ret = 1;
 111         }
 112
 113         if (!cpus_empty(mask)) {
 114                 /*
 115                  * It might be necessary to actually check whether the devices
 116                  * have different broadcast functions. For now, just use the
 117                  * one of the first device. This works as long as we have this
 118                  * misfeature only on x86 (lapic)
 119                  */
 120                 cpu = first_cpu(mask);
 121                 td = &per_cpu(tick_cpu_device, cpu);
 122                 td->evtdev->broadcast(mask);
 123                 ret = 1;
 124         }
 125         return ret;
 126 }
 127
 128 /*
 129  * Periodic broadcast:
 130  * - invoke the broadcast handlers
 131  */
 132 static void tick_do_periodic_broadcast(void)
 133 {
 134         cpumask_t mask;
 135
 136         spin_lock(&tick_broadcast_lock);
 137
 138         cpus_and(mask, cpu_online_map, tick_broadcast_mask);
 139         tick_do_broadcast(mask);
 140
 141         spin_unlock(&tick_broadcast_lock);
 142 }
 143
 144 /*
 145  * Event handler for periodic broadcast ticks
 146  */
 147 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 148 {
 149         dev->next_event.tv64 = KTIME_MAX;
 150
 151         tick_do_periodic_broadcast();
 152
 153         /*
 154          * The device is in periodic mode. No reprogramming necessary:
 155          */
 156         if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
 157                 return;
 158
 159         /*
 160          * Setup the next period for devices, which do not have
 161          * periodic mode:
 162          */
 163         for (;;) {
 164                 ktime_t next = ktime_add(dev->next_event, tick_period);
 165
 166                 if (!clockevents_program_event(dev, next, ktime_get()))
 167                         return;
 168                 tick_do_periodic_broadcast();
 169         }
 170 }
 171
 172 /*
 173  * Powerstate information: The system enters/leaves a state, where
 174  * affected devices might stop
 175  */
 176 static void tick_do_broadcast_on_off(void *why)
 177 {
 178         struct clock_event_device *bc, *dev;
 179         struct tick_device *td;
 180         unsigned long flags, *reason = why;
 181         int cpu;
 182
 183         spin_lock_irqsave(&tick_broadcast_lock, flags);
 184
 185         cpu = smp_processor_id();
 186         td = &per_cpu(tick_cpu_device, cpu);
 187         dev = td->evtdev;
 188         bc = tick_broadcast_device.evtdev;
 189
 190         /*
 191          * Is the device in broadcast mode forever or is it not
 192          * affected by the powerstate ?
 193          */
 194         if (!dev || !tick_device_is_functional(dev) ||
 195             !(dev->features & CLOCK_EVT_FEAT_C3STOP))
 196                 goto out;
 197
 198         if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_ON) {
 199                 if (!cpu_isset(cpu, tick_broadcast_mask)) {
 200                         cpu_set(cpu, tick_broadcast_mask);
 201                         if (td->mode == TICKDEV_MODE_PERIODIC)
 202                                 clockevents_set_mode(dev,
 203                                                      CLOCK_EVT_MODE_SHUTDOWN);
 204                 }
 205         } else {
 206                 if (cpu_isset(cpu, tick_broadcast_mask)) {
 207                         cpu_clear(cpu, tick_broadcast_mask);
 208                         if (td->mode == TICKDEV_MODE_PERIODIC)
 209                                 tick_setup_periodic(dev, 0);
 210                 }
 211         }
 212
 213         if (cpus_empty(tick_broadcast_mask))
 214                 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 215         else {
 216                 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 217                         tick_broadcast_start_periodic(bc);
 218         }
 219 out:
 220         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 221 }
 222
 223 /*
 224  * Powerstate information: The system enters/leaves a state, where
 225  * affected devices might stop.
 226  */
 227 void tick_broadcast_on_off(unsigned long reason, int *oncpu)
 228 {
 229         int cpu = get_cpu();
 230
 231         if (cpu == *oncpu)
 232                 tick_do_broadcast_on_off(&reason);
 233         else
 234                 smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
 235                                          &reason, 1, 1);
 236         put_cpu();
 237 }
 238
 239 /*
 240  * Set the periodic handler depending on broadcast on/off
 241  */
 242 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 243 {
 244         if (!broadcast)
 245                 dev->event_handler = tick_handle_periodic;
 246         else
 247                 dev->event_handler = tick_handle_periodic_broadcast;
 248 }
 249
 250 /*
 251  * Remove a CPU from broadcasting
 252  */
 253 void tick_shutdown_broadcast(unsigned int *cpup)
 254 {
 255         struct clock_event_device *bc;
 256         unsigned long flags;
 257         unsigned int cpu = *cpup;
 258
 259         spin_lock_irqsave(&tick_broadcast_lock, flags);
 260
 261         bc = tick_broadcast_device.evtdev;
 262         cpu_clear(cpu, tick_broadcast_mask);
 263
 264         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 265                 if (bc && cpus_empty(tick_broadcast_mask))
 266                         clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 267         }
 268
 269         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 270 }