xref: /linux/arch/powerpc/kernel/tau_6xx.c (revision 4413e16d9d21673bb5048a2e542f1aaa00015c2e)
1 /*
2  * temp.c	Thermal management for cpu's with Thermal Assist Units
3  *
4  * Written by Troy Benjegerdes <hozer@drgw.net>
5  *
6  * TODO:
7  * dynamic power management to limit peak CPU temp (using ICTC)
8  * calibration???
9  *
10  * Silly, crazy ideas: use cpu load (from scheduler) and ICTC to extend battery
11  * life in portables, and add a 'performance/watt' metric somewhere in /proc
12  */
13 
14 #include <linux/errno.h>
15 #include <linux/jiffies.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 
23 #include <asm/io.h>
24 #include <asm/reg.h>
25 #include <asm/nvram.h>
26 #include <asm/cache.h>
27 #include <asm/8xx_immap.h>
28 #include <asm/machdep.h>
29 
30 static struct tau_temp
31 {
32 	int interrupts;
33 	unsigned char low;
34 	unsigned char high;
35 	unsigned char grew;
36 } tau[NR_CPUS];
37 
38 struct timer_list tau_timer;
39 
40 #undef DEBUG
41 
42 /* TODO: put these in a /proc interface, with some sanity checks, and maybe
43  * dynamic adjustment to minimize # of interrupts */
44 /* configurable values for step size and how much to expand the window when
45  * we get an interrupt. These are based on the limit that was out of range */
46 #define step_size		2	/* step size when temp goes out of range */
47 #define window_expand		1	/* expand the window by this much */
48 /* configurable values for shrinking the window */
49 #define shrink_timer	2*HZ	/* period between shrinking the window */
50 #define min_window	2	/* minimum window size, degrees C */
51 
52 void set_thresholds(unsigned long cpu)
53 {
54 #ifdef CONFIG_TAU_INT
55 	/*
56 	 * setup THRM1,
57 	 * threshold, valid bit, enable interrupts, interrupt when below threshold
58 	 */
59 	mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TIE | THRM1_TID);
60 
61 	/* setup THRM2,
62 	 * threshold, valid bit, enable interrupts, interrupt when above threshold
63 	 */
64 	mtspr (SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | THRM1_TIE);
65 #else
66 	/* same thing but don't enable interrupts */
67 	mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TID);
68 	mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V);
69 #endif
70 }
71 
72 void TAUupdate(int cpu)
73 {
74 	unsigned thrm;
75 
76 #ifdef DEBUG
77 	printk("TAUupdate ");
78 #endif
79 
80 	/* if both thresholds are crossed, the step_sizes cancel out
81 	 * and the window winds up getting expanded twice. */
82 	if((thrm = mfspr(SPRN_THRM1)) & THRM1_TIV){ /* is valid? */
83 		if(thrm & THRM1_TIN){ /* crossed low threshold */
84 			if (tau[cpu].low >= step_size){
85 				tau[cpu].low -= step_size;
86 				tau[cpu].high -= (step_size - window_expand);
87 			}
88 			tau[cpu].grew = 1;
89 #ifdef DEBUG
90 			printk("low threshold crossed ");
91 #endif
92 		}
93 	}
94 	if((thrm = mfspr(SPRN_THRM2)) & THRM1_TIV){ /* is valid? */
95 		if(thrm & THRM1_TIN){ /* crossed high threshold */
96 			if (tau[cpu].high <= 127-step_size){
97 				tau[cpu].low += (step_size - window_expand);
98 				tau[cpu].high += step_size;
99 			}
100 			tau[cpu].grew = 1;
101 #ifdef DEBUG
102 			printk("high threshold crossed ");
103 #endif
104 		}
105 	}
106 
107 #ifdef DEBUG
108 	printk("grew = %d\n", tau[cpu].grew);
109 #endif
110 
111 #ifndef CONFIG_TAU_INT /* tau_timeout will do this if not using interrupts */
112 	set_thresholds(cpu);
113 #endif
114 
115 }
116 
117 #ifdef CONFIG_TAU_INT
118 /*
119  * TAU interrupts - called when we have a thermal assist unit interrupt
120  * with interrupts disabled
121  */
122 
123 void TAUException(struct pt_regs * regs)
124 {
125 	int cpu = smp_processor_id();
126 
127 	irq_enter();
128 	tau[cpu].interrupts++;
129 
130 	TAUupdate(cpu);
131 
132 	irq_exit();
133 }
134 #endif /* CONFIG_TAU_INT */
135 
136 static void tau_timeout(void * info)
137 {
138 	int cpu;
139 	unsigned long flags;
140 	int size;
141 	int shrink;
142 
143 	/* disabling interrupts *should* be okay */
144 	local_irq_save(flags);
145 	cpu = smp_processor_id();
146 
147 #ifndef CONFIG_TAU_INT
148 	TAUupdate(cpu);
149 #endif
150 
151 	size = tau[cpu].high - tau[cpu].low;
152 	if (size > min_window && ! tau[cpu].grew) {
153 		/* do an exponential shrink of half the amount currently over size */
154 		shrink = (2 + size - min_window) / 4;
155 		if (shrink) {
156 			tau[cpu].low += shrink;
157 			tau[cpu].high -= shrink;
158 		} else { /* size must have been min_window + 1 */
159 			tau[cpu].low += 1;
160 #if 1 /* debug */
161 			if ((tau[cpu].high - tau[cpu].low) != min_window){
162 				printk(KERN_ERR "temp.c: line %d, logic error\n", __LINE__);
163 			}
164 #endif
165 		}
166 	}
167 
168 	tau[cpu].grew = 0;
169 
170 	set_thresholds(cpu);
171 
172 	/*
173 	 * Do the enable every time, since otherwise a bunch of (relatively)
174 	 * complex sleep code needs to be added. One mtspr every time
175 	 * tau_timeout is called is probably not a big deal.
176 	 *
177 	 * Enable thermal sensor and set up sample interval timer
178 	 * need 20 us to do the compare.. until a nice 'cpu_speed' function
179 	 * call is implemented, just assume a 500 mhz clock. It doesn't really
180 	 * matter if we take too long for a compare since it's all interrupt
181 	 * driven anyway.
182 	 *
183 	 * use a extra long time.. (60 us @ 500 mhz)
184 	 */
185 	mtspr(SPRN_THRM3, THRM3_SITV(500*60) | THRM3_E);
186 
187 	local_irq_restore(flags);
188 }
189 
190 static void tau_timeout_smp(unsigned long unused)
191 {
192 
193 	/* schedule ourselves to be run again */
194 	mod_timer(&tau_timer, jiffies + shrink_timer) ;
195 	on_each_cpu(tau_timeout, NULL, 0);
196 }
197 
198 /*
199  * setup the TAU
200  *
201  * Set things up to use THRM1 as a temperature lower bound, and THRM2 as an upper bound.
202  * Start off at zero
203  */
204 
205 int tau_initialized = 0;
206 
207 void __init TAU_init_smp(void * info)
208 {
209 	unsigned long cpu = smp_processor_id();
210 
211 	/* set these to a reasonable value and let the timer shrink the
212 	 * window */
213 	tau[cpu].low = 5;
214 	tau[cpu].high = 120;
215 
216 	set_thresholds(cpu);
217 }
218 
219 int __init TAU_init(void)
220 {
221 	/* We assume in SMP that if one CPU has TAU support, they
222 	 * all have it --BenH
223 	 */
224 	if (!cpu_has_feature(CPU_FTR_TAU)) {
225 		printk("Thermal assist unit not available\n");
226 		tau_initialized = 0;
227 		return 1;
228 	}
229 
230 
231 	/* first, set up the window shrinking timer */
232 	init_timer(&tau_timer);
233 	tau_timer.function = tau_timeout_smp;
234 	tau_timer.expires = jiffies + shrink_timer;
235 	add_timer(&tau_timer);
236 
237 	on_each_cpu(TAU_init_smp, NULL, 0);
238 
239 	printk("Thermal assist unit ");
240 #ifdef CONFIG_TAU_INT
241 	printk("using interrupts, ");
242 #else
243 	printk("using timers, ");
244 #endif
245 	printk("shrink_timer: %d jiffies\n", shrink_timer);
246 	tau_initialized = 1;
247 
248 	return 0;
249 }
250 
251 __initcall(TAU_init);
252 
253 /*
254  * return current temp
255  */
256 
257 u32 cpu_temp_both(unsigned long cpu)
258 {
259 	return ((tau[cpu].high << 16) | tau[cpu].low);
260 }
261 
262 int cpu_temp(unsigned long cpu)
263 {
264 	return ((tau[cpu].high + tau[cpu].low) / 2);
265 }
266 
267 int tau_interrupts(unsigned long cpu)
268 {
269 	return (tau[cpu].interrupts);
270 }
271