2 * temp.c Thermal management for cpu's with Thermal Assist Units
4 * Written by Troy Benjegerdes <hozer@drgw.net>
7 * dynamic power management to limit peak CPU temp (using ICTC)
10 * Silly, crazy ideas: use cpu load (from scheduler) and ICTC to extend battery
11 * life in portables, and add a 'performance/watt' metric somewhere in /proc
14 #include <linux/errno.h>
15 #include <linux/jiffies.h>
16 #include <linux/kernel.h>
17 #include <linux/param.h>
18 #include <linux/string.h>
20 #include <linux/interrupt.h>
21 #include <linux/init.h>
25 #include <asm/nvram.h>
26 #include <asm/cache.h>
27 #include <asm/8xx_immap.h>
28 #include <asm/machdep.h>
30 static struct tau_temp
38 struct timer_list tau_timer;
40 /* TODO: put these in a /proc interface, with some sanity checks, and maybe
41 * dynamic adjustment to minimize # of interrupts */
42 /* configurable values for step size and how much to expand the window when
43 * we get an interrupt. These are based on the limit that was out of range */
44 #define step_size 2 /* step size when temp goes out of range */
45 #define window_expand 1 /* expand the window by this much */
46 /* configurable values for shrinking the window */
47 #define shrink_timer 2*HZ /* period between shrinking the window */
48 #define min_window 2 /* minimum window size, degrees C */
50 void set_thresholds(unsigned long cpu)
55 * threshold, valid bit, enable interrupts, interrupt when below threshold
57 mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TIE | THRM1_TID);
60 * threshold, valid bit, enable interrupts, interrupt when above threshold
62 mtspr (SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | THRM1_TIE);
64 /* same thing but don't enable interrupts */
65 mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TID);
66 mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V);
70 void TAUupdate(int cpu)
73 u32 bits = THRM1_TIV | THRM1_TIN | THRM1_V;
75 /* if both thresholds are crossed, the step_sizes cancel out
76 * and the window winds up getting expanded twice. */
77 thrm = mfspr(SPRN_THRM1);
78 if ((thrm & bits) == bits) {
81 if (tau[cpu].low >= step_size) {
82 tau[cpu].low -= step_size;
83 tau[cpu].high -= (step_size - window_expand);
86 pr_debug("%s: low threshold crossed\n", __func__);
88 thrm = mfspr(SPRN_THRM2);
89 if ((thrm & bits) == bits) {
92 if (tau[cpu].high <= 127 - step_size) {
93 tau[cpu].low += (step_size - window_expand);
94 tau[cpu].high += step_size;
97 pr_debug("%s: high threshold crossed\n", __func__);
101 #ifdef CONFIG_TAU_INT
103 * TAU interrupts - called when we have a thermal assist unit interrupt
104 * with interrupts disabled
107 void TAUException(struct pt_regs * regs)
109 int cpu = smp_processor_id();
112 tau[cpu].interrupts++;
118 #endif /* CONFIG_TAU_INT */
120 static void tau_timeout(void * info)
126 cpu = smp_processor_id();
128 #ifndef CONFIG_TAU_INT
132 /* Stop thermal sensor comparisons and interrupts */
133 mtspr(SPRN_THRM3, 0);
135 size = tau[cpu].high - tau[cpu].low;
136 if (size > min_window && ! tau[cpu].grew) {
137 /* do an exponential shrink of half the amount currently over size */
138 shrink = (2 + size - min_window) / 4;
140 tau[cpu].low += shrink;
141 tau[cpu].high -= shrink;
142 } else { /* size must have been min_window + 1 */
145 if ((tau[cpu].high - tau[cpu].low) != min_window){
146 printk(KERN_ERR "temp.c: line %d, logic error\n", __LINE__);
156 /* Restart thermal sensor comparisons and interrupts.
157 * The "PowerPC 740 and PowerPC 750 Microprocessor Datasheet"
158 * recommends that "the maximum value be set in THRM3 under all
161 mtspr(SPRN_THRM3, THRM3_SITV(0x1fff) | THRM3_E);
164 static void tau_timeout_smp(unsigned long unused)
167 /* schedule ourselves to be run again */
168 mod_timer(&tau_timer, jiffies + shrink_timer) ;
169 on_each_cpu(tau_timeout, NULL, 0);
175 * Set things up to use THRM1 as a temperature lower bound, and THRM2 as an upper bound.
179 int tau_initialized = 0;
181 void __init TAU_init_smp(void * info)
183 unsigned long cpu = smp_processor_id();
185 /* set these to a reasonable value and let the timer shrink the
193 int __init TAU_init(void)
195 /* We assume in SMP that if one CPU has TAU support, they
198 if (!cpu_has_feature(CPU_FTR_TAU)) {
199 printk("Thermal assist unit not available\n");
205 /* first, set up the window shrinking timer */
206 init_timer(&tau_timer);
207 tau_timer.function = tau_timeout_smp;
208 tau_timer.expires = jiffies + shrink_timer;
209 add_timer(&tau_timer);
211 on_each_cpu(TAU_init_smp, NULL, 0);
213 printk("Thermal assist unit ");
214 #ifdef CONFIG_TAU_INT
215 printk("using interrupts, ");
217 printk("using timers, ");
219 printk("shrink_timer: %d jiffies\n", shrink_timer);
225 __initcall(TAU_init);
228 * return current temp
231 u32 cpu_temp_both(unsigned long cpu)
233 return ((tau[cpu].high << 16) | tau[cpu].low);
236 int cpu_temp(unsigned long cpu)
238 return ((tau[cpu].high + tau[cpu].low) / 2);
241 int tau_interrupts(unsigned long cpu)
243 return (tau[cpu].interrupts);