1 // SPDX-License-Identifier: GPL-2.0
3 * temp.c Thermal management for cpu's with Thermal Assist Units
5 * Written by Troy Benjegerdes <hozer@drgw.net>
8 * dynamic power management to limit peak CPU temp (using ICTC)
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
15 #include <linux/errno.h>
16 #include <linux/kernel.h>
17 #include <linux/param.h>
18 #include <linux/string.h>
20 #include <linux/interrupt.h>
21 #include <linux/init.h>
22 #include <linux/delay.h>
23 #include <linux/workqueue.h>
25 #include <asm/interrupt.h>
28 #include <asm/nvram.h>
29 #include <asm/cache.h>
30 #include <asm/8xx_immap.h>
31 #include <asm/machdep.h>
32 #include <asm/asm-prototypes.h>
36 static struct tau_temp
44 static bool tau_int_enable;
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 2000 /* period between shrinking the window */
54 #define min_window 2 /* minimum window size, degrees C */
56 static void set_thresholds(unsigned long cpu)
58 u32 maybe_tie = tau_int_enable ? THRM1_TIE : 0;
60 /* setup THRM1, threshold, valid bit, interrupt when below threshold */
61 mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | maybe_tie | THRM1_TID);
63 /* setup THRM2, threshold, valid bit, interrupt when above threshold */
64 mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | maybe_tie);
67 static void TAUupdate(int cpu)
70 u32 bits = THRM1_TIV | THRM1_TIN | THRM1_V;
72 /* if both thresholds are crossed, the step_sizes cancel out
73 * and the window winds up getting expanded twice. */
74 thrm = mfspr(SPRN_THRM1);
75 if ((thrm & bits) == bits) {
78 if (tau[cpu].low >= step_size) {
79 tau[cpu].low -= step_size;
80 tau[cpu].high -= (step_size - window_expand);
83 pr_debug("%s: low threshold crossed\n", __func__);
85 thrm = mfspr(SPRN_THRM2);
86 if ((thrm & bits) == bits) {
89 if (tau[cpu].high <= 127 - step_size) {
90 tau[cpu].low += (step_size - window_expand);
91 tau[cpu].high += step_size;
94 pr_debug("%s: high threshold crossed\n", __func__);
100 * TAU interrupts - called when we have a thermal assist unit interrupt
101 * with interrupts disabled
104 DEFINE_INTERRUPT_HANDLER_ASYNC(TAUException)
106 int cpu = smp_processor_id();
108 tau[cpu].interrupts++;
112 #endif /* CONFIG_TAU_INT */
114 static void tau_timeout(void * info)
120 cpu = smp_processor_id();
125 /* Stop thermal sensor comparisons and interrupts */
126 mtspr(SPRN_THRM3, 0);
128 size = tau[cpu].high - tau[cpu].low;
129 if (size > min_window && ! tau[cpu].grew) {
130 /* do an exponential shrink of half the amount currently over size */
131 shrink = (2 + size - min_window) / 4;
133 tau[cpu].low += shrink;
134 tau[cpu].high -= shrink;
135 } else { /* size must have been min_window + 1 */
138 if ((tau[cpu].high - tau[cpu].low) != min_window){
139 printk(KERN_ERR "temp.c: line %d, logic error\n", __LINE__);
149 /* Restart thermal sensor comparisons and interrupts.
150 * The "PowerPC 740 and PowerPC 750 Microprocessor Datasheet"
151 * recommends that "the maximum value be set in THRM3 under all
154 mtspr(SPRN_THRM3, THRM3_SITV(0x1fff) | THRM3_E);
157 static struct workqueue_struct *tau_workq;
159 static void tau_work_func(struct work_struct *work)
161 msleep(shrink_timer);
162 on_each_cpu(tau_timeout, NULL, 0);
163 /* schedule ourselves to be run again */
164 queue_work(tau_workq, work);
167 static DECLARE_WORK(tau_work, tau_work_func);
172 * Set things up to use THRM1 as a temperature lower bound, and THRM2 as an upper bound.
176 int tau_initialized = 0;
178 static void __init TAU_init_smp(void *info)
180 unsigned long cpu = smp_processor_id();
182 /* set these to a reasonable value and let the timer shrink the
190 static int __init TAU_init(void)
192 /* We assume in SMP that if one CPU has TAU support, they
195 if (!cpu_has_feature(CPU_FTR_TAU)) {
196 printk("Thermal assist unit not available\n");
201 tau_int_enable = IS_ENABLED(CONFIG_TAU_INT) &&
202 !strcmp(cur_cpu_spec->platform, "ppc750");
204 tau_workq = alloc_workqueue("tau", WQ_UNBOUND, 1);
208 on_each_cpu(TAU_init_smp, NULL, 0);
210 queue_work(tau_workq, &tau_work);
212 pr_info("Thermal assist unit using %s, shrink_timer: %d ms\n",
213 tau_int_enable ? "interrupts" : "workqueue", shrink_timer);
219 __initcall(TAU_init);
222 * return current temp
225 u32 cpu_temp_both(unsigned long cpu)
227 return ((tau[cpu].high << 16) | tau[cpu].low);
230 u32 cpu_temp(unsigned long cpu)
232 return ((tau[cpu].high + tau[cpu].low) / 2);
235 u32 tau_interrupts(unsigned long cpu)
237 return (tau[cpu].interrupts);