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(tau_timeout, NULL, 0);
162	/* schedule ourselves to be run again */
163	queue_work(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(TAU_init_smp, NULL, 0);
208
209	queue_work(tau_workq, &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