arch/powerpc/kernel/tau_6xx.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/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 }