arch/ppc/kernel/temp.c

   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/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>
  20 #include <linux/mm.h>
  21 #include <linux/interrupt.h>
  22 #include <linux/init.h>
  23
  24 #include <asm/segment.h>
  25 #include <asm/io.h>
  26 #include <asm/reg.h>
  27 #include <asm/nvram.h>
  28 #include <asm/cache.h>
  29 #include <asm/8xx_immap.h>
  30 #include <asm/machdep.h>
  31
  32 static struct tau_temp
  33 {
  34         int interrupts;
  35         unsigned char low;
  36         unsigned char high;
  37         unsigned char grew;
  38 } tau[NR_CPUS];
  39
  40 struct timer_list tau_timer;
  41
  42 #undef DEBUG
  43
  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 */
  53
  54 void set_thresholds(unsigned long cpu)
  55 {
  56 #ifdef CONFIG_TAU_INT
  57         /*
  58          * setup THRM1,
  59          * threshold, valid bit, enable interrupts, interrupt when below threshold
  60          */
  61         mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TIE | THRM1_TID);
  62
  63         /* setup THRM2,
  64          * threshold, valid bit, enable interrupts, interrupt when above threshhold
  65          */
  66         mtspr (SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | THRM1_TIE);
  67 #else
  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);
  71 #endif
  72 }
  73
  74 void TAUupdate(int cpu)
  75 {
  76         unsigned thrm;
  77
  78 #ifdef DEBUG
  79         printk("TAUupdate ");
  80 #endif
  81
  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);
  89                         }
  90                         tau[cpu].grew = 1;
  91 #ifdef DEBUG
  92                         printk("low threshold crossed ");
  93 #endif
  94                 }
  95         }
  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;
 101                         }
 102                         tau[cpu].grew = 1;
 103 #ifdef DEBUG
 104                         printk("high threshold crossed ");
 105 #endif
 106                 }
 107         }
 108
 109 #ifdef DEBUG
 110         printk("grew = %d\n", tau[cpu].grew);
 111 #endif
 112
 113 #ifndef CONFIG_TAU_INT /* tau_timeout will do this if not using interrupts */
 114         set_thresholds(cpu);
 115 #endif
 116
 117 }
 118
 119 #ifdef CONFIG_TAU_INT
 120 /*
 121  * TAU interrupts - called when we have a thermal assist unit interrupt
 122  * with interrupts disabled
 123  */
 124
 125 void TAUException(struct pt_regs * regs)
 126 {
 127         int cpu = smp_processor_id();
 128
 129         irq_enter();
 130         tau[cpu].interrupts++;
 131
 132         TAUupdate(cpu);
 133
 134         irq_exit();
 135 }
 136 #endif /* CONFIG_TAU_INT */
 137
 138 static void tau_timeout(void * info)
 139 {
 140         int cpu;
 141         unsigned long flags;
 142         int size;
 143         int shrink;
 144
 145         /* disabling interrupts *should* be okay */
 146         local_irq_save(flags);
 147         cpu = smp_processor_id();
 148
 149 #ifndef CONFIG_TAU_INT
 150         TAUupdate(cpu);
 151 #endif
 152
 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;
 157                 if (shrink) {
 158                         tau[cpu].low += shrink;
 159                         tau[cpu].high -= shrink;
 160                 } else { /* size must have been min_window + 1 */
 161                         tau[cpu].low += 1;
 162 #if 1 /* debug */
 163                         if ((tau[cpu].high - tau[cpu].low) != min_window){
 164                                 printk(KERN_ERR "temp.c: line %d, logic error\n", __LINE__);
 165                         }
 166 #endif
 167                 }
 168         }
 169
 170         tau[cpu].grew = 0;
 171
 172         set_thresholds(cpu);
 173
 174         /*
 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.
 178          *
 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
 183          * driven anyway.
 184          *
 185          * use a extra long time.. (60 us @ 500 mhz)
 186          */
 187         mtspr(SPRN_THRM3, THRM3_SITV(500*60) | THRM3_E);
 188
 189         local_irq_restore(flags);
 190 }
 191
 192 static void tau_timeout_smp(unsigned long unused)
 193 {
 194
 195         /* schedule ourselves to be run again */
 196         mod_timer(&tau_timer, jiffies + shrink_timer) ;
 197         on_each_cpu(tau_timeout, NULL, 1, 0);
 198 }
 199
 200 /*
 201  * setup the TAU
 202  *
 203  * Set things up to use THRM1 as a temperature lower bound, and THRM2 as an upper bound.
 204  * Start off at zero
 205  */
 206
 207 int tau_initialized = 0;
 208
 209 void __init TAU_init_smp(void * info)
 210 {
 211         unsigned long cpu = smp_processor_id();
 212
 213         /* set these to a reasonable value and let the timer shrink the
 214          * window */
 215         tau[cpu].low = 5;
 216         tau[cpu].high = 120;
 217
 218         set_thresholds(cpu);
 219 }
 220
 221 int __init TAU_init(void)
 222 {
 223         /* We assume in SMP that if one CPU has TAU support, they
 224          * all have it --BenH
 225          */
 226         if (!cpu_has_feature(CPU_FTR_TAU)) {
 227                 printk("Thermal assist unit not available\n");
 228                 tau_initialized = 0;
 229                 return 1;
 230         }
 231
 232
 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);
 238
 239         on_each_cpu(TAU_init_smp, NULL, 1, 0);
 240
 241         printk("Thermal assist unit ");
 242 #ifdef CONFIG_TAU_INT
 243         printk("using interrupts, ");
 244 #else
 245         printk("using timers, ");
 246 #endif
 247         printk("shrink_timer: %d jiffies\n", shrink_timer);
 248         tau_initialized = 1;
 249
 250         return 0;
 251 }
 252
 253 __initcall(TAU_init);
 254
 255 /*
 256  * return current temp
 257  */
 258
 259 u32 cpu_temp_both(unsigned long cpu)
 260 {
 261         return ((tau[cpu].high << 16) | tau[cpu].low);
 262 }
 263
 264 int cpu_temp(unsigned long cpu)
 265 {
 266         return ((tau[cpu].high + tau[cpu].low) / 2);
 267 }
 268
 269 int tau_interrupts(unsigned long cpu)
 270 {
 271         return (tau[cpu].interrupts);
 272 }