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/interrupt.h>
26#include <asm/io.h>
27#include <asm/reg.h>
28#include <asm/nvram.h>
29#include <asm/cache.h>
30#include <asm/8xx_immap.h>
31#include <asm/machdep.h>
32
33#include "setup.h"
34
35static struct tau_temp
36{
37 int interrupts;
38 unsigned char low;
39 unsigned char high;
40 unsigned char grew;
41} tau[NR_CPUS];
42
43static 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
55static 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
66static 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
103DEFINE_INTERRUPT_HANDLER_ASYNC(TAUException)
104{
105 int cpu = smp_processor_id();
106
107 tau[cpu].interrupts++;
108
109 TAUupdate(cpu);
110}
111#endif /* CONFIG_TAU_INT */
112
113static void tau_timeout(void * info)
114{
115 int cpu;
116 int size;
117 int shrink;
118
119 cpu = smp_processor_id();
120
121 if (!tau_int_enable)
122 TAUupdate(cpu);
123
124 /* Stop thermal sensor comparisons and interrupts */
125 mtspr(SPRN_THRM3, 0);
126
127 size = tau[cpu].high - tau[cpu].low;
128 if (size > min_window && ! tau[cpu].grew) {
129 /* do an exponential shrink of half the amount currently over size */
130 shrink = (2 + size - min_window) / 4;
131 if (shrink) {
132 tau[cpu].low += shrink;
133 tau[cpu].high -= shrink;
134 } else { /* size must have been min_window + 1 */
135 tau[cpu].low += 1;
136#if 1 /* debug */
137 if ((tau[cpu].high - tau[cpu].low) != min_window){
138 printk(KERN_ERR "temp.c: line %d, logic error\n", __LINE__);
139 }
140#endif
141 }
142 }
143
144 tau[cpu].grew = 0;
145
146 set_thresholds(cpu);
147
148 /* Restart thermal sensor comparisons and interrupts.
149 * The "PowerPC 740 and PowerPC 750 Microprocessor Datasheet"
150 * recommends that "the maximum value be set in THRM3 under all
151 * conditions."
152 */
153 mtspr(SPRN_THRM3, THRM3_SITV(0x1fff) | THRM3_E);
154}
155
156static struct workqueue_struct *tau_workq;
157
158static void tau_work_func(struct work_struct *work)
159{
160 msleep(shrink_timer);
161 on_each_cpu(func: tau_timeout, NULL, wait: 0);
162 /* schedule ourselves to be run again */
163 queue_work(wq: tau_workq, work);
164}
165
166static DECLARE_WORK(tau_work, tau_work_func);
167
168/*
169 * setup the TAU
170 *
171 * Set things up to use THRM1 as a temperature lower bound, and THRM2 as an upper bound.
172 * Start off at zero
173 */
174
175int tau_initialized = 0;
176
177static void __init TAU_init_smp(void *info)
178{
179 unsigned long cpu = smp_processor_id();
180
181 /* set these to a reasonable value and let the timer shrink the
182 * window */
183 tau[cpu].low = 5;
184 tau[cpu].high = 120;
185
186 set_thresholds(cpu);
187}
188
189static int __init TAU_init(void)
190{
191 /* We assume in SMP that if one CPU has TAU support, they
192 * all have it --BenH
193 */
194 if (!cpu_has_feature(CPU_FTR_TAU)) {
195 printk("Thermal assist unit not available\n");
196 tau_initialized = 0;
197 return 1;
198 }
199
200 tau_int_enable = IS_ENABLED(CONFIG_TAU_INT) &&
201 !strcmp(cur_cpu_spec->platform, "ppc750");
202
203 tau_workq = alloc_ordered_workqueue("tau", 0);
204 if (!tau_workq)
205 return -ENOMEM;
206
207 on_each_cpu(func: TAU_init_smp, NULL, wait: 0);
208
209 queue_work(wq: tau_workq, work: &tau_work);
210
211 pr_info("Thermal assist unit using %s, shrink_timer: %d ms\n",
212 tau_int_enable ? "interrupts" : "workqueue", shrink_timer);
213 tau_initialized = 1;
214
215 return 0;
216}
217
218__initcall(TAU_init);
219
220/*
221 * return current temp
222 */
223
224u32 cpu_temp_both(unsigned long cpu)
225{
226 return ((tau[cpu].high << 16) | tau[cpu].low);
227}
228
229u32 cpu_temp(unsigned long cpu)
230{
231 return ((tau[cpu].high + tau[cpu].low) / 2);
232}
233
234u32 tau_interrupts(unsigned long cpu)
235{
236 return (tau[cpu].interrupts);
237}
238

source code of linux/arch/powerpc/kernel/tau_6xx.c