arch/powerpc/kernel/tau_6xx.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * temp.c       Thermal management for cpu's with Thermal Assist Units
   4  *
   5  * Written by Troy Benjegerdes <hozer@drgw.net>
   6  *
   7  * TODO:
   8  * dynamic power management to limit peak CPU temp (using ICTC)
   9  * calibration???
  10  *
  11  * Silly, crazy ideas: use cpu load (from scheduler) and ICTC to extend battery
  12  * life in portables, and add a 'performance/watt' metric somewhere in /proc
  13  */
  14
  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/io.h>
  25 #include <asm/reg.h>
  26 #include <asm/nvram.h>
  27 #include <asm/cache.h>
  28 #include <asm/8xx_immap.h>
  29 #include <asm/machdep.h>
  30
  31 static struct tau_temp
  32 {
  33         int interrupts;
  34         unsigned char low;
  35         unsigned char high;
  36         unsigned char grew;
  37 } tau[NR_CPUS];
  38
  39 struct timer_list tau_timer;
  40
  41 #undef DEBUG
  42
  43 /* TODO: put these in a /proc interface, with some sanity checks, and maybe
  44  * dynamic adjustment to minimize # of interrupts */
  45 /* configurable values for step size and how much to expand the window when
  46  * we get an interrupt. These are based on the limit that was out of range */
  47 #define step_size               2       /* step size when temp goes out of range */
  48 #define window_expand           1       /* expand the window by this much */
  49 /* configurable values for shrinking the window */
  50 #define shrink_timer    2*HZ    /* period between shrinking the window */
  51 #define min_window      2       /* minimum window size, degrees C */
  52
  53 void set_thresholds(unsigned long cpu)
  54 {
  55 #ifdef CONFIG_TAU_INT
  56         /*
  57          * setup THRM1,
  58          * threshold, valid bit, enable interrupts, interrupt when below threshold
  59          */
  60         mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TIE | THRM1_TID);
  61
  62         /* setup THRM2,
  63          * threshold, valid bit, enable interrupts, interrupt when above threshold
  64          */
  65         mtspr (SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | THRM1_TIE);
  66 #else
  67         /* same thing but don't enable interrupts */
  68         mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TID);
  69         mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V);
  70 #endif
  71 }
  72
  73 void TAUupdate(int cpu)
  74 {
  75         unsigned thrm;
  76
  77 #ifdef DEBUG
  78         printk("TAUupdate ");
  79 #endif
  80
  81         /* if both thresholds are crossed, the step_sizes cancel out
  82          * and the window winds up getting expanded twice. */
  83         if((thrm = mfspr(SPRN_THRM1)) & THRM1_TIV){ /* is valid? */
  84                 if(thrm & THRM1_TIN){ /* crossed low threshold */
  85                         if (tau[cpu].low >= step_size){
  86                                 tau[cpu].low -= step_size;
  87                                 tau[cpu].high -= (step_size - window_expand);
  88                         }
  89                         tau[cpu].grew = 1;
  90 #ifdef DEBUG
  91                         printk("low threshold crossed ");
  92 #endif
  93                 }
  94         }
  95         if((thrm = mfspr(SPRN_THRM2)) & THRM1_TIV){ /* is valid? */
  96                 if(thrm & THRM1_TIN){ /* crossed high threshold */
  97                         if (tau[cpu].high <= 127-step_size){
  98                                 tau[cpu].low += (step_size - window_expand);
  99                                 tau[cpu].high += step_size;
 100                         }
 101                         tau[cpu].grew = 1;
 102 #ifdef DEBUG
 103                         printk("high threshold crossed ");
 104 #endif
 105                 }
 106         }
 107
 108 #ifdef DEBUG
 109         printk("grew = %d\n", tau[cpu].grew);
 110 #endif
 111
 112 #ifndef CONFIG_TAU_INT /* tau_timeout will do this if not using interrupts */
 113         set_thresholds(cpu);
 114 #endif
 115
 116 }
 117
 118 #ifdef CONFIG_TAU_INT
 119 /*
 120  * TAU interrupts - called when we have a thermal assist unit interrupt
 121  * with interrupts disabled
 122  */
 123
 124 void TAUException(struct pt_regs * regs)
 125 {
 126         int cpu = smp_processor_id();
 127
 128         irq_enter();
 129         tau[cpu].interrupts++;
 130
 131         TAUupdate(cpu);
 132
 133         irq_exit();
 134 }
 135 #endif /* CONFIG_TAU_INT */
 136
 137 static void tau_timeout(void * info)
 138 {
 139         int cpu;
 140         unsigned long flags;
 141         int size;
 142         int shrink;
 143
 144         /* disabling interrupts *should* be okay */
 145         local_irq_save(flags);
 146         cpu = smp_processor_id();
 147
 148 #ifndef CONFIG_TAU_INT
 149         TAUupdate(cpu);
 150 #endif
 151
 152         size = tau[cpu].high - tau[cpu].low;
 153         if (size > min_window && ! tau[cpu].grew) {
 154                 /* do an exponential shrink of half the amount currently over size */
 155                 shrink = (2 + size - min_window) / 4;
 156                 if (shrink) {
 157                         tau[cpu].low += shrink;
 158                         tau[cpu].high -= shrink;
 159                 } else { /* size must have been min_window + 1 */
 160                         tau[cpu].low += 1;
 161 #if 1 /* debug */
 162                         if ((tau[cpu].high - tau[cpu].low) != min_window){
 163                                 printk(KERN_ERR "temp.c: line %d, logic error\n", __LINE__);
 164                         }
 165 #endif
 166                 }
 167         }
 168
 169         tau[cpu].grew = 0;
 170
 171         set_thresholds(cpu);
 172
 173         /*
 174          * Do the enable every time, since otherwise a bunch of (relatively)
 175          * complex sleep code needs to be added. One mtspr every time
 176          * tau_timeout is called is probably not a big deal.
 177          *
 178          * Enable thermal sensor and set up sample interval timer
 179          * need 20 us to do the compare.. until a nice 'cpu_speed' function
 180          * call is implemented, just assume a 500 mhz clock. It doesn't really
 181          * matter if we take too long for a compare since it's all interrupt
 182          * driven anyway.
 183          *
 184          * use a extra long time.. (60 us @ 500 mhz)
 185          */
 186         mtspr(SPRN_THRM3, THRM3_SITV(500*60) | THRM3_E);
 187
 188         local_irq_restore(flags);
 189 }
 190
 191 static void tau_timeout_smp(struct timer_list *unused)
 192 {
 193
 194         /* schedule ourselves to be run again */
 195         mod_timer(&tau_timer, jiffies + shrink_timer) ;
 196         on_each_cpu(tau_timeout, NULL, 0);
 197 }
 198
 199 /*
 200  * setup the TAU
 201  *
 202  * Set things up to use THRM1 as a temperature lower bound, and THRM2 as an upper bound.
 203  * Start off at zero
 204  */
 205
 206 int tau_initialized = 0;
 207
 208 void __init TAU_init_smp(void * info)
 209 {
 210         unsigned long cpu = smp_processor_id();
 211
 212         /* set these to a reasonable value and let the timer shrink the
 213          * window */
 214         tau[cpu].low = 5;
 215         tau[cpu].high = 120;
 216
 217         set_thresholds(cpu);
 218 }
 219
 220 int __init TAU_init(void)
 221 {
 222         /* We assume in SMP that if one CPU has TAU support, they
 223          * all have it --BenH
 224          */
 225         if (!cpu_has_feature(CPU_FTR_TAU)) {
 226                 printk("Thermal assist unit not available\n");
 227                 tau_initialized = 0;
 228                 return 1;
 229         }
 230
 231
 232         /* first, set up the window shrinking timer */
 233         timer_setup(&tau_timer, tau_timeout_smp, 0);
 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 }