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
set_thresholds(unsigned long cpu)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
TAUupdate(int cpu)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
TAUException(struct pt_regs * regs)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
tau_timeout(void * info)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
tau_work_func(struct work_struct * work)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
TAU_init_smp(void * info)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
TAU_init(void)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
cpu_temp_both(unsigned long cpu)227 u32 cpu_temp_both(unsigned long cpu)
228 {
229 return ((tau[cpu].high << 16) | tau[cpu].low);
230 }
231
cpu_temp(unsigned long cpu)232 u32 cpu_temp(unsigned long cpu)
233 {
234 return ((tau[cpu].high + tau[cpu].low) / 2);
235 }
236
tau_interrupts(unsigned long cpu)237 u32 tau_interrupts(unsigned long cpu)
238 {
239 return (tau[cpu].interrupts);
240 }
241