1 /*
2 * temp.c Thermal management for cpu's with Thermal Assist Units
3 *
4 * Written by Troy Benjegerdes <hozer@drgw.net>
5 *
6 * TODO:
7 * dynamic power management to limit peak CPU temp (using ICTC)
8 * calibration???
9 *
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
12 */
13
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>
19 #include <linux/mm.h>
20 #include <linux/interrupt.h>
21 #include <linux/init.h>
22
23 #include <asm/io.h>
24 #include <asm/reg.h>
25 #include <asm/nvram.h>
26 #include <asm/cache.h>
27 #include <asm/8xx_immap.h>
28 #include <asm/machdep.h>
29
30 static struct tau_temp
31 {
32 int interrupts;
33 unsigned char low;
34 unsigned char high;
35 unsigned char grew;
36 } tau[NR_CPUS];
37
38 struct timer_list tau_timer;
39
40 #undef DEBUG
41
42 /* TODO: put these in a /proc interface, with some sanity checks, and maybe
43 * dynamic adjustment to minimize # of interrupts */
44 /* configurable values for step size and how much to expand the window when
45 * we get an interrupt. These are based on the limit that was out of range */
46 #define step_size 2 /* step size when temp goes out of range */
47 #define window_expand 1 /* expand the window by this much */
48 /* configurable values for shrinking the window */
49 #define shrink_timer 2*HZ /* period between shrinking the window */
50 #define min_window 2 /* minimum window size, degrees C */
51
set_thresholds(unsigned long cpu)52 void set_thresholds(unsigned long cpu)
53 {
54 #ifdef CONFIG_TAU_INT
55 /*
56 * setup THRM1,
57 * threshold, valid bit, enable interrupts, interrupt when below threshold
58 */
59 mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TIE | THRM1_TID);
60
61 /* setup THRM2,
62 * threshold, valid bit, enable interrupts, interrupt when above threshhold
63 */
64 mtspr (SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | THRM1_TIE);
65 #else
66 /* same thing but don't enable interrupts */
67 mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TID);
68 mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V);
69 #endif
70 }
71
TAUupdate(int cpu)72 void TAUupdate(int cpu)
73 {
74 unsigned thrm;
75
76 #ifdef DEBUG
77 printk("TAUupdate ");
78 #endif
79
80 /* if both thresholds are crossed, the step_sizes cancel out
81 * and the window winds up getting expanded twice. */
82 if((thrm = mfspr(SPRN_THRM1)) & THRM1_TIV){ /* is valid? */
83 if(thrm & THRM1_TIN){ /* crossed low threshold */
84 if (tau[cpu].low >= step_size){
85 tau[cpu].low -= step_size;
86 tau[cpu].high -= (step_size - window_expand);
87 }
88 tau[cpu].grew = 1;
89 #ifdef DEBUG
90 printk("low threshold crossed ");
91 #endif
92 }
93 }
94 if((thrm = mfspr(SPRN_THRM2)) & THRM1_TIV){ /* is valid? */
95 if(thrm & THRM1_TIN){ /* crossed high threshold */
96 if (tau[cpu].high <= 127-step_size){
97 tau[cpu].low += (step_size - window_expand);
98 tau[cpu].high += step_size;
99 }
100 tau[cpu].grew = 1;
101 #ifdef DEBUG
102 printk("high threshold crossed ");
103 #endif
104 }
105 }
106
107 #ifdef DEBUG
108 printk("grew = %d\n", tau[cpu].grew);
109 #endif
110
111 #ifndef CONFIG_TAU_INT /* tau_timeout will do this if not using interrupts */
112 set_thresholds(cpu);
113 #endif
114
115 }
116
117 #ifdef CONFIG_TAU_INT
118 /*
119 * TAU interrupts - called when we have a thermal assist unit interrupt
120 * with interrupts disabled
121 */
122
TAUException(struct pt_regs * regs)123 void TAUException(struct pt_regs * regs)
124 {
125 int cpu = smp_processor_id();
126
127 irq_enter();
128 tau[cpu].interrupts++;
129
130 TAUupdate(cpu);
131
132 irq_exit();
133 }
134 #endif /* CONFIG_TAU_INT */
135
tau_timeout(void * info)136 static void tau_timeout(void * info)
137 {
138 int cpu;
139 unsigned long flags;
140 int size;
141 int shrink;
142
143 /* disabling interrupts *should* be okay */
144 local_irq_save(flags);
145 cpu = smp_processor_id();
146
147 #ifndef CONFIG_TAU_INT
148 TAUupdate(cpu);
149 #endif
150
151 size = tau[cpu].high - tau[cpu].low;
152 if (size > min_window && ! tau[cpu].grew) {
153 /* do an exponential shrink of half the amount currently over size */
154 shrink = (2 + size - min_window) / 4;
155 if (shrink) {
156 tau[cpu].low += shrink;
157 tau[cpu].high -= shrink;
158 } else { /* size must have been min_window + 1 */
159 tau[cpu].low += 1;
160 #if 1 /* debug */
161 if ((tau[cpu].high - tau[cpu].low) != min_window){
162 printk(KERN_ERR "temp.c: line %d, logic error\n", __LINE__);
163 }
164 #endif
165 }
166 }
167
168 tau[cpu].grew = 0;
169
170 set_thresholds(cpu);
171
172 /*
173 * Do the enable every time, since otherwise a bunch of (relatively)
174 * complex sleep code needs to be added. One mtspr every time
175 * tau_timeout is called is probably not a big deal.
176 *
177 * Enable thermal sensor and set up sample interval timer
178 * need 20 us to do the compare.. until a nice 'cpu_speed' function
179 * call is implemented, just assume a 500 mhz clock. It doesn't really
180 * matter if we take too long for a compare since it's all interrupt
181 * driven anyway.
182 *
183 * use a extra long time.. (60 us @ 500 mhz)
184 */
185 mtspr(SPRN_THRM3, THRM3_SITV(500*60) | THRM3_E);
186
187 local_irq_restore(flags);
188 }
189
tau_timeout_smp(unsigned long unused)190 static void tau_timeout_smp(unsigned long unused)
191 {
192
193 /* schedule ourselves to be run again */
194 mod_timer(&tau_timer, jiffies + shrink_timer) ;
195 on_each_cpu(tau_timeout, NULL, 0);
196 }
197
198 /*
199 * setup the TAU
200 *
201 * Set things up to use THRM1 as a temperature lower bound, and THRM2 as an upper bound.
202 * Start off at zero
203 */
204
205 int tau_initialized = 0;
206
TAU_init_smp(void * info)207 void __init TAU_init_smp(void * info)
208 {
209 unsigned long cpu = smp_processor_id();
210
211 /* set these to a reasonable value and let the timer shrink the
212 * window */
213 tau[cpu].low = 5;
214 tau[cpu].high = 120;
215
216 set_thresholds(cpu);
217 }
218
TAU_init(void)219 int __init TAU_init(void)
220 {
221 /* We assume in SMP that if one CPU has TAU support, they
222 * all have it --BenH
223 */
224 if (!cpu_has_feature(CPU_FTR_TAU)) {
225 printk("Thermal assist unit not available\n");
226 tau_initialized = 0;
227 return 1;
228 }
229
230
231 /* first, set up the window shrinking timer */
232 init_timer(&tau_timer);
233 tau_timer.function = tau_timeout_smp;
234 tau_timer.expires = jiffies + shrink_timer;
235 add_timer(&tau_timer);
236
237 on_each_cpu(TAU_init_smp, NULL, 0);
238
239 printk("Thermal assist unit ");
240 #ifdef CONFIG_TAU_INT
241 printk("using interrupts, ");
242 #else
243 printk("using timers, ");
244 #endif
245 printk("shrink_timer: %d jiffies\n", shrink_timer);
246 tau_initialized = 1;
247
248 return 0;
249 }
250
251 __initcall(TAU_init);
252
253 /*
254 * return current temp
255 */
256
cpu_temp_both(unsigned long cpu)257 u32 cpu_temp_both(unsigned long cpu)
258 {
259 return ((tau[cpu].high << 16) | tau[cpu].low);
260 }
261
cpu_temp(unsigned long cpu)262 int cpu_temp(unsigned long cpu)
263 {
264 return ((tau[cpu].high + tau[cpu].low) / 2);
265 }
266
tau_interrupts(unsigned long cpu)267 int tau_interrupts(unsigned long cpu)
268 {
269 return (tau[cpu].interrupts);
270 }
271