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Linux/arch/powerpc/kernel/tau_6xx.c

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  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 
 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 threshold
 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 
 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 
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 
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 
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 
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 
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 
257 u32 cpu_temp_both(unsigned long cpu)
258 {
259         return ((tau[cpu].high << 16) | tau[cpu].low);
260 }
261 
262 int cpu_temp(unsigned long cpu)
263 {
264         return ((tau[cpu].high + tau[cpu].low) / 2);
265 }
266 
267 int tau_interrupts(unsigned long cpu)
268 {
269         return (tau[cpu].interrupts);
270 }
271 

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