x86: remove pointless comments
[linux-2.6.git] / arch / x86 / kernel / cpu / mcheck / therm_throt.c
1 /*
2  *
3  * Thermal throttle event support code (such as syslog messaging and rate
4  * limiting) that was factored out from x86_64 (mce_intel.c) and i386 (p4.c).
5  * This allows consistent reporting of CPU thermal throttle events.
6  *
7  * Maintains a counter in /sys that keeps track of the number of thermal
8  * events, such that the user knows how bad the thermal problem might be
9  * (since the logging to syslog and mcelog is rate limited).
10  *
11  * Author: Dmitriy Zavin (dmitriyz@google.com)
12  *
13  * Credits: Adapted from Zwane Mwaikambo's original code in mce_intel.c.
14  *          Inspired by Ross Biro's and Al Borchers' counter code.
15  */
16
17 #include <linux/percpu.h>
18 #include <linux/sysdev.h>
19 #include <linux/cpu.h>
20 #include <asm/cpu.h>
21 #include <linux/notifier.h>
22 #include <linux/jiffies.h>
23 #include <asm/therm_throt.h>
24
25 /* How long to wait between reporting thermal events */
26 #define CHECK_INTERVAL              (300 * HZ)
27
28 static DEFINE_PER_CPU(__u64, next_check) = INITIAL_JIFFIES;
29 static DEFINE_PER_CPU(unsigned long, thermal_throttle_count);
30 atomic_t therm_throt_en = ATOMIC_INIT(0);
31
32 #ifdef CONFIG_SYSFS
33 #define define_therm_throt_sysdev_one_ro(_name)                              \
34         static SYSDEV_ATTR(_name, 0444, therm_throt_sysdev_show_##_name, NULL)
35
36 #define define_therm_throt_sysdev_show_func(name)                            \
37 static ssize_t therm_throt_sysdev_show_##name(struct sys_device *dev,        \
38                                               char *buf)                     \
39 {                                                                            \
40         unsigned int cpu = dev->id;                                          \
41         ssize_t ret;                                                         \
42                                                                              \
43         preempt_disable();              /* CPU hotplug */                    \
44         if (cpu_online(cpu))                                                 \
45                 ret = sprintf(buf, "%lu\n",                                  \
46                               per_cpu(thermal_throttle_##name, cpu));        \
47         else                                                                 \
48                 ret = 0;                                                     \
49         preempt_enable();                                                    \
50                                                                              \
51         return ret;                                                          \
52 }
53
54 define_therm_throt_sysdev_show_func(count);
55 define_therm_throt_sysdev_one_ro(count);
56
57 static struct attribute *thermal_throttle_attrs[] = {
58         &attr_count.attr,
59         NULL
60 };
61
62 static struct attribute_group thermal_throttle_attr_group = {
63         .attrs = thermal_throttle_attrs,
64         .name = "thermal_throttle"
65 };
66 #endif /* CONFIG_SYSFS */
67
68 /***
69  * therm_throt_process - Process thermal throttling event from interrupt
70  * @curr: Whether the condition is current or not (boolean), since the
71  *        thermal interrupt normally gets called both when the thermal
72  *        event begins and once the event has ended.
73  *
74  * This function is called by the thermal interrupt after the
75  * IRQ has been acknowledged.
76  *
77  * It will take care of rate limiting and printing messages to the syslog.
78  *
79  * Returns: 0 : Event should NOT be further logged, i.e. still in
80  *              "timeout" from previous log message.
81  *          1 : Event should be logged further, and a message has been
82  *              printed to the syslog.
83  */
84 int therm_throt_process(int curr)
85 {
86         unsigned int cpu = smp_processor_id();
87         __u64 tmp_jiffs = get_jiffies_64();
88
89         if (curr)
90                 __get_cpu_var(thermal_throttle_count)++;
91
92         if (time_before64(tmp_jiffs, __get_cpu_var(next_check)))
93                 return 0;
94
95         __get_cpu_var(next_check) = tmp_jiffs + CHECK_INTERVAL;
96
97         /* if we just entered the thermal event */
98         if (curr) {
99                 printk(KERN_CRIT "CPU%d: Temperature above threshold, "
100                        "cpu clock throttled (total events = %lu)\n", cpu,
101                        __get_cpu_var(thermal_throttle_count));
102
103                 add_taint(TAINT_MACHINE_CHECK);
104         } else {
105                 printk(KERN_CRIT "CPU%d: Temperature/speed normal\n", cpu);
106         }
107
108         return 1;
109 }
110
111 #ifdef CONFIG_SYSFS
112 /* Add/Remove thermal_throttle interface for CPU device */
113 static __cpuinit int thermal_throttle_add_dev(struct sys_device *sys_dev)
114 {
115         return sysfs_create_group(&sys_dev->kobj, &thermal_throttle_attr_group);
116 }
117
118 static __cpuinit void thermal_throttle_remove_dev(struct sys_device *sys_dev)
119 {
120         sysfs_remove_group(&sys_dev->kobj, &thermal_throttle_attr_group);
121 }
122
123 /* Mutex protecting device creation against CPU hotplug */
124 static DEFINE_MUTEX(therm_cpu_lock);
125
126 /* Get notified when a cpu comes on/off. Be hotplug friendly. */
127 static __cpuinit int thermal_throttle_cpu_callback(struct notifier_block *nfb,
128                                                    unsigned long action,
129                                                    void *hcpu)
130 {
131         unsigned int cpu = (unsigned long)hcpu;
132         struct sys_device *sys_dev;
133         int err = 0;
134
135         sys_dev = get_cpu_sysdev(cpu);
136         switch (action) {
137         case CPU_UP_PREPARE:
138         case CPU_UP_PREPARE_FROZEN:
139                 mutex_lock(&therm_cpu_lock);
140                 err = thermal_throttle_add_dev(sys_dev);
141                 mutex_unlock(&therm_cpu_lock);
142                 WARN_ON(err);
143                 break;
144         case CPU_UP_CANCELED:
145         case CPU_UP_CANCELED_FROZEN:
146         case CPU_DEAD:
147         case CPU_DEAD_FROZEN:
148                 mutex_lock(&therm_cpu_lock);
149                 thermal_throttle_remove_dev(sys_dev);
150                 mutex_unlock(&therm_cpu_lock);
151                 break;
152         }
153         return err ? NOTIFY_BAD : NOTIFY_OK;
154 }
155
156 static struct notifier_block thermal_throttle_cpu_notifier __cpuinitdata =
157 {
158         .notifier_call = thermal_throttle_cpu_callback,
159 };
160
161 static __init int thermal_throttle_init_device(void)
162 {
163         unsigned int cpu = 0;
164         int err;
165
166         if (!atomic_read(&therm_throt_en))
167                 return 0;
168
169         register_hotcpu_notifier(&thermal_throttle_cpu_notifier);
170
171 #ifdef CONFIG_HOTPLUG_CPU
172         mutex_lock(&therm_cpu_lock);
173 #endif
174         /* connect live CPUs to sysfs */
175         for_each_online_cpu(cpu) {
176                 err = thermal_throttle_add_dev(get_cpu_sysdev(cpu));
177                 WARN_ON(err);
178         }
179 #ifdef CONFIG_HOTPLUG_CPU
180         mutex_unlock(&therm_cpu_lock);
181 #endif
182
183         return 0;
184 }
185
186 device_initcall(thermal_throttle_init_device);
187 #endif /* CONFIG_SYSFS */