xref: /openbmc/linux/arch/powerpc/kernel/tau_6xx.c (revision bd545224)
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 
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 
DEFINE_INTERRUPT_HANDLER_ASYNC(TAUException)103 DEFINE_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 
tau_timeout(void * info)113 static 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 
156 static struct workqueue_struct *tau_workq;
157 
tau_work_func(struct work_struct * work)158 static 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 
166 static 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 
175 int tau_initialized = 0;
176 
TAU_init_smp(void * info)177 static 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 
TAU_init(void)189 static 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 
cpu_temp_both(unsigned long cpu)224 u32 cpu_temp_both(unsigned long cpu)
225 {
226 	return ((tau[cpu].high << 16) | tau[cpu].low);
227 }
228 
cpu_temp(unsigned long cpu)229 u32 cpu_temp(unsigned long cpu)
230 {
231 	return ((tau[cpu].high + tau[cpu].low) / 2);
232 }
233 
tau_interrupts(unsigned long cpu)234 u32 tau_interrupts(unsigned long cpu)
235 {
236 	return (tau[cpu].interrupts);
237 }
238