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/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 #include <linux/delay.h>
  23 #include <linux/workqueue.h>
  24
  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 #include <asm/asm-prototypes.h>
  32
  33 #include "setup.h"
  34
  35 static struct tau_temp
  36 {
  37         int interrupts;
  38         unsigned char low;
  39         unsigned char high;
  40         unsigned char grew;
  41 } tau[NR_CPUS];
  42
  43 static bool tau_int_enable;
  44
  45 /* TODO: put these in a /proc interface, with some sanity checks, and maybe
  46  * dynamic adjustment to minimize # of interrupts */
  47 /* configurable values for step size and how much to expand the window when
  48  * we get an interrupt. These are based on the limit that was out of range */
  49 #define step_size               2       /* step size when temp goes out of range */
  50 #define window_expand           1       /* expand the window by this much */
  51 /* configurable values for shrinking the window */
  52 #define shrink_timer    2000    /* period between shrinking the window */
  53 #define min_window      2       /* minimum window size, degrees C */
  54
  55 static void set_thresholds(unsigned long cpu)
  56 {
  57         u32 maybe_tie = tau_int_enable ? THRM1_TIE : 0;
  58
  59         /* setup THRM1, threshold, valid bit, interrupt when below threshold */
  60         mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | maybe_tie | THRM1_TID);
  61
  62         /* setup THRM2, threshold, valid bit, interrupt when above threshold */
  63         mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | maybe_tie);
  64 }
  65
  66 static void TAUupdate(int cpu)
  67 {
  68         u32 thrm;
  69         u32 bits = THRM1_TIV | THRM1_TIN | THRM1_V;
  70
  71         /* if both thresholds are crossed, the step_sizes cancel out
  72          * and the window winds up getting expanded twice. */
  73         thrm = mfspr(SPRN_THRM1);
  74         if ((thrm & bits) == bits) {
  75                 mtspr(SPRN_THRM1, 0);
  76
  77                 if (tau[cpu].low >= step_size) {
  78                         tau[cpu].low -= step_size;
  79                         tau[cpu].high -= (step_size - window_expand);
  80                 }
  81                 tau[cpu].grew = 1;
  82                 pr_debug("%s: low threshold crossed\n", __func__);
  83         }
  84         thrm = mfspr(SPRN_THRM2);
  85         if ((thrm & bits) == bits) {
  86                 mtspr(SPRN_THRM2, 0);
  87
  88                 if (tau[cpu].high <= 127 - step_size) {
  89                         tau[cpu].low += (step_size - window_expand);
  90                         tau[cpu].high += step_size;
  91                 }
  92                 tau[cpu].grew = 1;
  93                 pr_debug("%s: high threshold crossed\n", __func__);
  94         }
  95 }
  96
  97 #ifdef CONFIG_TAU_INT
  98 /*
  99  * TAU interrupts - called when we have a thermal assist unit interrupt
 100  * with interrupts disabled
 101  */
 102
 103 void TAUException(struct pt_regs * regs)
 104 {
 105         int cpu = smp_processor_id();
 106
 107         irq_enter();
 108         tau[cpu].interrupts++;
 109
 110         TAUupdate(cpu);
 111
 112         irq_exit();
 113 }
 114 #endif /* CONFIG_TAU_INT */
 115
 116 static void tau_timeout(void * info)
 117 {
 118         int cpu;
 119         int size;
 120         int shrink;
 121
 122         cpu = smp_processor_id();
 123
 124         if (!tau_int_enable)
 125                 TAUupdate(cpu);
 126
 127         /* Stop thermal sensor comparisons and interrupts */
 128         mtspr(SPRN_THRM3, 0);
 129
 130         size = tau[cpu].high - tau[cpu].low;
 131         if (size > min_window && ! tau[cpu].grew) {
 132                 /* do an exponential shrink of half the amount currently over size */
 133                 shrink = (2 + size - min_window) / 4;
 134                 if (shrink) {
 135                         tau[cpu].low += shrink;
 136                         tau[cpu].high -= shrink;
 137                 } else { /* size must have been min_window + 1 */
 138                         tau[cpu].low += 1;
 139 #if 1 /* debug */
 140                         if ((tau[cpu].high - tau[cpu].low) != min_window){
 141                                 printk(KERN_ERR "temp.c: line %d, logic error\n", __LINE__);
 142                         }
 143 #endif
 144                 }
 145         }
 146
 147         tau[cpu].grew = 0;
 148
 149         set_thresholds(cpu);
 150
 151         /* Restart thermal sensor comparisons and interrupts.
 152          * The "PowerPC 740 and PowerPC 750 Microprocessor Datasheet"
 153          * recommends that "the maximum value be set in THRM3 under all
 154          * conditions."
 155          */
 156         mtspr(SPRN_THRM3, THRM3_SITV(0x1fff) | THRM3_E);
 157 }
 158
 159 static struct workqueue_struct *tau_workq;
 160
 161 static void tau_work_func(struct work_struct *work)
 162 {
 163         msleep(shrink_timer);
 164         on_each_cpu(tau_timeout, NULL, 0);
 165         /* schedule ourselves to be run again */
 166         queue_work(tau_workq, work);
 167 }
 168
 169 DECLARE_WORK(tau_work, tau_work_func);
 170
 171 /*
 172  * setup the TAU
 173  *
 174  * Set things up to use THRM1 as a temperature lower bound, and THRM2 as an upper bound.
 175  * Start off at zero
 176  */
 177
 178 int tau_initialized = 0;
 179
 180 static void __init TAU_init_smp(void *info)
 181 {
 182         unsigned long cpu = smp_processor_id();
 183
 184         /* set these to a reasonable value and let the timer shrink the
 185          * window */
 186         tau[cpu].low = 5;
 187         tau[cpu].high = 120;
 188
 189         set_thresholds(cpu);
 190 }
 191
 192 static int __init TAU_init(void)
 193 {
 194         /* We assume in SMP that if one CPU has TAU support, they
 195          * all have it --BenH
 196          */
 197         if (!cpu_has_feature(CPU_FTR_TAU)) {
 198                 printk("Thermal assist unit not available\n");
 199                 tau_initialized = 0;
 200                 return 1;
 201         }
 202
 203         tau_int_enable = IS_ENABLED(CONFIG_TAU_INT) &&
 204                          !strcmp(cur_cpu_spec->platform, "ppc750");
 205
 206         tau_workq = alloc_workqueue("tau", WQ_UNBOUND, 1, 0);
 207         if (!tau_workq)
 208                 return -ENOMEM;
 209
 210         on_each_cpu(TAU_init_smp, NULL, 0);
 211
 212         queue_work(tau_workq, &tau_work);
 213
 214         pr_info("Thermal assist unit using %s, shrink_timer: %d ms\n",
 215                 tau_int_enable ? "interrupts" : "workqueue", shrink_timer);
 216         tau_initialized = 1;
 217
 218         return 0;
 219 }
 220
 221 __initcall(TAU_init);
 222
 223 /*
 224  * return current temp
 225  */
 226
 227 u32 cpu_temp_both(unsigned long cpu)
 228 {
 229         return ((tau[cpu].high << 16) | tau[cpu].low);
 230 }
 231
 232 u32 cpu_temp(unsigned long cpu)
 233 {
 234         return ((tau[cpu].high + tau[cpu].low) / 2);
 235 }
 236
 237 u32 tau_interrupts(unsigned long cpu)
 238 {
 239         return (tau[cpu].interrupts);
 240 }