root/arch/powerpc/kernel/tau_6xx.c

DEFINITIONS

1. set_thresholds
2. TAUupdate
3. TAUException
4. tau_timeout
5. tau_timeout_smp
6. TAU_init_smp
7. TAU_init
8. cpu_temp_both
9. cpu_temp
10. tau_interrupts

   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 #include <asm/asm-prototypes.h>
  31 
  32 #include "setup.h"
  33 
  34 static struct tau_temp
  35 {
  36         int interrupts;
  37         unsigned char low;
  38         unsigned char high;
  39         unsigned char grew;
  40 } tau[NR_CPUS];
  41 
  42 struct timer_list tau_timer;
  43 
  44 #undef DEBUG
  45 
  46 /* TODO: put these in a /proc interface, with some sanity checks, and maybe
  47  * dynamic adjustment to minimize # of interrupts */
  48 /* configurable values for step size and how much to expand the window when
  49  * we get an interrupt. These are based on the limit that was out of range */
  50 #define step_size               2       /* step size when temp goes out of range */
  51 #define window_expand           1       /* expand the window by this much */
  52 /* configurable values for shrinking the window */
  53 #define shrink_timer    2*HZ    /* period between shrinking the window */
  54 #define min_window      2       /* minimum window size, degrees C */
  55 
  56 static void set_thresholds(unsigned long cpu)
  57 {
  58 #ifdef CONFIG_TAU_INT
  59         /*
  60          * setup THRM1,
  61          * threshold, valid bit, enable interrupts, interrupt when below threshold
  62          */
  63         mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TIE | THRM1_TID);
  64 
  65         /* setup THRM2,
  66          * threshold, valid bit, enable interrupts, interrupt when above threshold
  67          */
  68         mtspr (SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | THRM1_TIE);
  69 #else
  70         /* same thing but don't enable interrupts */
  71         mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TID);
  72         mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V);
  73 #endif
  74 }
  75 
  76 static void TAUupdate(int cpu)
  77 {
  78         unsigned thrm;
  79 
  80 #ifdef DEBUG
  81         printk("TAUupdate ");
  82 #endif
  83 
  84         /* if both thresholds are crossed, the step_sizes cancel out
  85          * and the window winds up getting expanded twice. */
  86         if((thrm = mfspr(SPRN_THRM1)) & THRM1_TIV){ /* is valid? */
  87                 if(thrm & THRM1_TIN){ /* crossed low threshold */
  88                         if (tau[cpu].low >= step_size){
  89                                 tau[cpu].low -= step_size;
  90                                 tau[cpu].high -= (step_size - window_expand);
  91                         }
  92                         tau[cpu].grew = 1;
  93 #ifdef DEBUG
  94                         printk("low threshold crossed ");
  95 #endif
  96                 }
  97         }
  98         if((thrm = mfspr(SPRN_THRM2)) & THRM1_TIV){ /* is valid? */
  99                 if(thrm & THRM1_TIN){ /* crossed high threshold */
 100                         if (tau[cpu].high <= 127-step_size){
 101                                 tau[cpu].low += (step_size - window_expand);
 102                                 tau[cpu].high += step_size;
 103                         }
 104                         tau[cpu].grew = 1;
 105 #ifdef DEBUG
 106                         printk("high threshold crossed ");
 107 #endif
 108                 }
 109         }
 110 
 111 #ifdef DEBUG
 112         printk("grew = %d\n", tau[cpu].grew);
 113 #endif
 114 
 115 #ifndef CONFIG_TAU_INT /* tau_timeout will do this if not using interrupts */
 116         set_thresholds(cpu);
 117 #endif
 118 
 119 }
 120 
 121 #ifdef CONFIG_TAU_INT
 122 /*
 123  * TAU interrupts - called when we have a thermal assist unit interrupt
 124  * with interrupts disabled
 125  */
 126 
 127 void TAUException(struct pt_regs * regs)
 128 {
 129         int cpu = smp_processor_id();
 130 
 131         irq_enter();
 132         tau[cpu].interrupts++;
 133 
 134         TAUupdate(cpu);
 135 
 136         irq_exit();
 137 }
 138 #endif /* CONFIG_TAU_INT */
 139 
 140 static void tau_timeout(void * info)
 141 {
 142         int cpu;
 143         unsigned long flags;
 144         int size;
 145         int shrink;
 146 
 147         /* disabling interrupts *should* be okay */
 148         local_irq_save(flags);
 149         cpu = smp_processor_id();
 150 
 151 #ifndef CONFIG_TAU_INT
 152         TAUupdate(cpu);
 153 #endif
 154 
 155         size = tau[cpu].high - tau[cpu].low;
 156         if (size > min_window && ! tau[cpu].grew) {
 157                 /* do an exponential shrink of half the amount currently over size */
 158                 shrink = (2 + size - min_window) / 4;
 159                 if (shrink) {
 160                         tau[cpu].low += shrink;
 161                         tau[cpu].high -= shrink;
 162                 } else { /* size must have been min_window + 1 */
 163                         tau[cpu].low += 1;
 164 #if 1 /* debug */
 165                         if ((tau[cpu].high - tau[cpu].low) != min_window){
 166                                 printk(KERN_ERR "temp.c: line %d, logic error\n", __LINE__);
 167                         }
 168 #endif
 169                 }
 170         }
 171 
 172         tau[cpu].grew = 0;
 173 
 174         set_thresholds(cpu);
 175 
 176         /*
 177          * Do the enable every time, since otherwise a bunch of (relatively)
 178          * complex sleep code needs to be added. One mtspr every time
 179          * tau_timeout is called is probably not a big deal.
 180          *
 181          * Enable thermal sensor and set up sample interval timer
 182          * need 20 us to do the compare.. until a nice 'cpu_speed' function
 183          * call is implemented, just assume a 500 mhz clock. It doesn't really
 184          * matter if we take too long for a compare since it's all interrupt
 185          * driven anyway.
 186          *
 187          * use a extra long time.. (60 us @ 500 mhz)
 188          */
 189         mtspr(SPRN_THRM3, THRM3_SITV(500*60) | THRM3_E);
 190 
 191         local_irq_restore(flags);
 192 }
 193 
 194 static void tau_timeout_smp(struct timer_list *unused)
 195 {
 196 
 197         /* schedule ourselves to be run again */
 198         mod_timer(&tau_timer, jiffies + shrink_timer) ;
 199         on_each_cpu(tau_timeout, NULL, 0);
 200 }
 201 
 202 /*
 203  * setup the TAU
 204  *
 205  * Set things up to use THRM1 as a temperature lower bound, and THRM2 as an upper bound.
 206  * Start off at zero
 207  */
 208 
 209 int tau_initialized = 0;
 210 
 211 static void __init TAU_init_smp(void *info)
 212 {
 213         unsigned long cpu = smp_processor_id();
 214 
 215         /* set these to a reasonable value and let the timer shrink the
 216          * window */
 217         tau[cpu].low = 5;
 218         tau[cpu].high = 120;
 219 
 220         set_thresholds(cpu);
 221 }
 222 
 223 static int __init TAU_init(void)
 224 {
 225         /* We assume in SMP that if one CPU has TAU support, they
 226          * all have it --BenH
 227          */
 228         if (!cpu_has_feature(CPU_FTR_TAU)) {
 229                 printk("Thermal assist unit not available\n");
 230                 tau_initialized = 0;
 231                 return 1;
 232         }
 233 
 234 
 235         /* first, set up the window shrinking timer */
 236         timer_setup(&tau_timer, tau_timeout_smp, 0);
 237         tau_timer.expires = jiffies + shrink_timer;
 238         add_timer(&tau_timer);
 239 
 240         on_each_cpu(TAU_init_smp, NULL, 0);
 241 
 242         printk("Thermal assist unit ");
 243 #ifdef CONFIG_TAU_INT
 244         printk("using interrupts, ");
 245 #else
 246         printk("using timers, ");
 247 #endif
 248         printk("shrink_timer: %d jiffies\n", shrink_timer);
 249         tau_initialized = 1;
 250 
 251         return 0;
 252 }
 253 
 254 __initcall(TAU_init);
 255 
 256 /*
 257  * return current temp
 258  */
 259 
 260 u32 cpu_temp_both(unsigned long cpu)
 261 {
 262         return ((tau[cpu].high << 16) | tau[cpu].low);
 263 }
 264 
 265 u32 cpu_temp(unsigned long cpu)
 266 {
 267         return ((tau[cpu].high + tau[cpu].low) / 2);
 268 }
 269 
 270 u32 tau_interrupts(unsigned long cpu)
 271 {
 272         return (tau[cpu].interrupts);
 273 }