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
30static struct tau_temp
31{
32	int interrupts;
33	unsigned char low;
34	unsigned char high;
35	unsigned char grew;
36} tau[NR_CPUS];
37
38struct 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
52void 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
72void 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
123void 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
136static 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
190static 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
205int tau_initialized = 0;
206
207void __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
219int __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
257u32 cpu_temp_both(unsigned long cpu)
258{
259	return ((tau[cpu].high << 16) | tau[cpu].low);
260}
261
262int cpu_temp(unsigned long cpu)
263{
264	return ((tau[cpu].high + tau[cpu].low) / 2);
265}
266
267int tau_interrupts(unsigned long cpu)
268{
269	return (tau[cpu].interrupts);
270}
271