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/config.h>
15 #include <linux/errno.h>
16 #include <linux/jiffies.h>
17 #include <linux/kernel.h>
18 #include <linux/param.h>
19 #include <linux/string.h>
21 #include <linux/interrupt.h>
22 #include <linux/init.h>
24 #include <asm/segment.h>
27 #include <asm/nvram.h>
28 #include <asm/cache.h>
29 #include <asm/8xx_immap.h>
30 #include <asm/machdep.h>
32 static struct tau_temp
40 struct timer_list tau_timer;
44 /* TODO: put these in a /proc interface, with some sanity checks, and maybe
45 * dynamic adjustment to minimize # of interrupts */
46 /* configurable values for step size and how much to expand the window when
47 * we get an interrupt. These are based on the limit that was out of range */
48 #define step_size 2 /* step size when temp goes out of range */
49 #define window_expand 1 /* expand the window by this much */
50 /* configurable values for shrinking the window */
51 #define shrink_timer 2*HZ /* period between shrinking the window */
52 #define min_window 2 /* minimum window size, degrees C */
54 void set_thresholds(unsigned long cpu)
59 * threshold, valid bit, enable interrupts, interrupt when below threshold
61 mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TIE | THRM1_TID);
64 * threshold, valid bit, enable interrupts, interrupt when above threshhold
66 mtspr (SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | THRM1_TIE);
68 /* same thing but don't enable interrupts */
69 mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TID);
70 mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V);
74 void TAUupdate(int cpu)
82 /* if both thresholds are crossed, the step_sizes cancel out
83 * and the window winds up getting expanded twice. */
84 if((thrm = mfspr(SPRN_THRM1)) & THRM1_TIV){ /* is valid? */
85 if(thrm & THRM1_TIN){ /* crossed low threshold */
86 if (tau[cpu].low >= step_size){
87 tau[cpu].low -= step_size;
88 tau[cpu].high -= (step_size - window_expand);
92 printk("low threshold crossed ");
96 if((thrm = mfspr(SPRN_THRM2)) & THRM1_TIV){ /* is valid? */
97 if(thrm & THRM1_TIN){ /* crossed high threshold */
98 if (tau[cpu].high <= 127-step_size){
99 tau[cpu].low += (step_size - window_expand);
100 tau[cpu].high += step_size;
104 printk("high threshold crossed ");
110 printk("grew = %d\n", tau[cpu].grew);
113 #ifndef CONFIG_TAU_INT /* tau_timeout will do this if not using interrupts */
119 #ifdef CONFIG_TAU_INT
121 * TAU interrupts - called when we have a thermal assist unit interrupt
122 * with interrupts disabled
125 void TAUException(struct pt_regs * regs)
127 int cpu = smp_processor_id();
130 tau[cpu].interrupts++;
136 #endif /* CONFIG_TAU_INT */
138 static void tau_timeout(void * info)
145 /* disabling interrupts *should* be okay */
146 local_irq_save(flags);
147 cpu = smp_processor_id();
149 #ifndef CONFIG_TAU_INT
153 size = tau[cpu].high - tau[cpu].low;
154 if (size > min_window && ! tau[cpu].grew) {
155 /* do an exponential shrink of half the amount currently over size */
156 shrink = (2 + size - min_window) / 4;
158 tau[cpu].low += shrink;
159 tau[cpu].high -= shrink;
160 } else { /* size must have been min_window + 1 */
163 if ((tau[cpu].high - tau[cpu].low) != min_window){
164 printk(KERN_ERR "temp.c: line %d, logic error\n", __LINE__);
175 * Do the enable every time, since otherwise a bunch of (relatively)
176 * complex sleep code needs to be added. One mtspr every time
177 * tau_timeout is called is probably not a big deal.
179 * Enable thermal sensor and set up sample interval timer
180 * need 20 us to do the compare.. until a nice 'cpu_speed' function
181 * call is implemented, just assume a 500 mhz clock. It doesn't really
182 * matter if we take too long for a compare since it's all interrupt
185 * use a extra long time.. (60 us @ 500 mhz)
187 mtspr(SPRN_THRM3, THRM3_SITV(500*60) | THRM3_E);
189 local_irq_restore(flags);
192 static void tau_timeout_smp(unsigned long unused)
195 /* schedule ourselves to be run again */
196 mod_timer(&tau_timer, jiffies + shrink_timer) ;
197 on_each_cpu(tau_timeout, NULL, 1, 0);
203 * Set things up to use THRM1 as a temperature lower bound, and THRM2 as an upper bound.
207 int tau_initialized = 0;
209 void __init TAU_init_smp(void * info)
211 unsigned long cpu = smp_processor_id();
213 /* set these to a reasonable value and let the timer shrink the
221 int __init TAU_init(void)
223 /* We assume in SMP that if one CPU has TAU support, they
226 if (!cpu_has_feature(CPU_FTR_TAU)) {
227 printk("Thermal assist unit not available\n");
233 /* first, set up the window shrinking timer */
234 init_timer(&tau_timer);
235 tau_timer.function = tau_timeout_smp;
236 tau_timer.expires = jiffies + shrink_timer;
237 add_timer(&tau_timer);
239 on_each_cpu(TAU_init_smp, NULL, 1, 0);
241 printk("Thermal assist unit ");
242 #ifdef CONFIG_TAU_INT
243 printk("using interrupts, ");
245 printk("using timers, ");
247 printk("shrink_timer: %d jiffies\n", shrink_timer);
253 __initcall(TAU_init);
256 * return current temp
259 u32 cpu_temp_both(unsigned long cpu)
261 return ((tau[cpu].high << 16) | tau[cpu].low);
264 int cpu_temp(unsigned long cpu)
266 return ((tau[cpu].high + tau[cpu].low) / 2);
269 int tau_interrupts(unsigned long cpu)
271 return (tau[cpu].interrupts);