xref: /openbmc/linux/drivers/watchdog/booke_wdt.c (revision c819e2cf)
1 /*
2  * Watchdog timer for PowerPC Book-E systems
3  *
4  * Author: Matthew McClintock
5  * Maintainer: Kumar Gala <galak@kernel.crashing.org>
6  *
7  * Copyright 2005, 2008, 2010-2011 Freescale Semiconductor Inc.
8  *
9  * This program is free software; you can redistribute  it and/or modify it
10  * under  the terms of  the GNU General  Public License as published by the
11  * Free Software Foundation;  either version 2 of the  License, or (at your
12  * option) any later version.
13  */
14 
15 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
16 
17 #include <linux/module.h>
18 #include <linux/smp.h>
19 #include <linux/watchdog.h>
20 
21 #include <asm/reg_booke.h>
22 #include <asm/time.h>
23 #include <asm/div64.h>
24 
25 /* If the kernel parameter wdt=1, the watchdog will be enabled at boot.
26  * Also, the wdt_period sets the watchdog timer period timeout.
27  * For E500 cpus the wdt_period sets which bit changing from 0->1 will
28  * trigger a watchog timeout. This watchdog timeout will occur 3 times, the
29  * first time nothing will happen, the second time a watchdog exception will
30  * occur, and the final time the board will reset.
31  */
32 
33 
34 #ifdef	CONFIG_PPC_FSL_BOOK3E
35 #define WDTP(x)		((((x)&0x3)<<30)|(((x)&0x3c)<<15))
36 #define WDTP_MASK	(WDTP(0x3f))
37 #else
38 #define WDTP(x)		(TCR_WP(x))
39 #define WDTP_MASK	(TCR_WP_MASK)
40 #endif
41 
42 static bool booke_wdt_enabled;
43 module_param(booke_wdt_enabled, bool, 0);
44 static int  booke_wdt_period = CONFIG_BOOKE_WDT_DEFAULT_TIMEOUT;
45 module_param(booke_wdt_period, int, 0);
46 
47 #ifdef CONFIG_PPC_FSL_BOOK3E
48 
49 /* For the specified period, determine the number of seconds
50  * corresponding to the reset time.  There will be a watchdog
51  * exception at approximately 3/5 of this time.
52  *
53  * The formula to calculate this is given by:
54  * 2.5 * (2^(63-period+1)) / timebase_freq
55  *
56  * In order to simplify things, we assume that period is
57  * at least 1.  This will still result in a very long timeout.
58  */
59 static unsigned long long period_to_sec(unsigned int period)
60 {
61 	unsigned long long tmp = 1ULL << (64 - period);
62 	unsigned long tmp2 = ppc_tb_freq;
63 
64 	/* tmp may be a very large number and we don't want to overflow,
65 	 * so divide the timebase freq instead of multiplying tmp
66 	 */
67 	tmp2 = tmp2 / 5 * 2;
68 
69 	do_div(tmp, tmp2);
70 	return tmp;
71 }
72 
73 /*
74  * This procedure will find the highest period which will give a timeout
75  * greater than the one required. e.g. for a bus speed of 66666666 and
76  * and a parameter of 2 secs, then this procedure will return a value of 38.
77  */
78 static unsigned int sec_to_period(unsigned int secs)
79 {
80 	unsigned int period;
81 	for (period = 63; period > 0; period--) {
82 		if (period_to_sec(period) >= secs)
83 			return period;
84 	}
85 	return 0;
86 }
87 
88 #define MAX_WDT_TIMEOUT		period_to_sec(1)
89 
90 #else /* CONFIG_PPC_FSL_BOOK3E */
91 
92 static unsigned long long period_to_sec(unsigned int period)
93 {
94 	return period;
95 }
96 
97 static unsigned int sec_to_period(unsigned int secs)
98 {
99 	return secs;
100 }
101 
102 #define MAX_WDT_TIMEOUT		3	/* from Kconfig */
103 
104 #endif /* !CONFIG_PPC_FSL_BOOK3E */
105 
106 static void __booke_wdt_set(void *data)
107 {
108 	u32 val;
109 	struct watchdog_device *wdog = data;
110 
111 	val = mfspr(SPRN_TCR);
112 	val &= ~WDTP_MASK;
113 	val |= WDTP(sec_to_period(wdog->timeout));
114 
115 	mtspr(SPRN_TCR, val);
116 }
117 
118 static void booke_wdt_set(void *data)
119 {
120 	on_each_cpu(__booke_wdt_set, data, 0);
121 }
122 
123 static void __booke_wdt_ping(void *data)
124 {
125 	mtspr(SPRN_TSR, TSR_ENW|TSR_WIS);
126 }
127 
128 static int booke_wdt_ping(struct watchdog_device *wdog)
129 {
130 	on_each_cpu(__booke_wdt_ping, NULL, 0);
131 
132 	return 0;
133 }
134 
135 static void __booke_wdt_enable(void *data)
136 {
137 	u32 val;
138 	struct watchdog_device *wdog = data;
139 
140 	/* clear status before enabling watchdog */
141 	__booke_wdt_ping(NULL);
142 	val = mfspr(SPRN_TCR);
143 	val &= ~WDTP_MASK;
144 	val |= (TCR_WIE|TCR_WRC(WRC_CHIP)|WDTP(sec_to_period(wdog->timeout)));
145 
146 	mtspr(SPRN_TCR, val);
147 }
148 
149 /**
150  * booke_wdt_disable - disable the watchdog on the given CPU
151  *
152  * This function is called on each CPU.  It disables the watchdog on that CPU.
153  *
154  * TCR[WRC] cannot be changed once it has been set to non-zero, but we can
155  * effectively disable the watchdog by setting its period to the maximum value.
156  */
157 static void __booke_wdt_disable(void *data)
158 {
159 	u32 val;
160 
161 	val = mfspr(SPRN_TCR);
162 	val &= ~(TCR_WIE | WDTP_MASK);
163 	mtspr(SPRN_TCR, val);
164 
165 	/* clear status to make sure nothing is pending */
166 	__booke_wdt_ping(NULL);
167 
168 }
169 
170 static int booke_wdt_start(struct watchdog_device *wdog)
171 {
172 	on_each_cpu(__booke_wdt_enable, wdog, 0);
173 	pr_debug("watchdog enabled (timeout = %u sec)\n", wdog->timeout);
174 
175 	return 0;
176 }
177 
178 static int booke_wdt_stop(struct watchdog_device *wdog)
179 {
180 	on_each_cpu(__booke_wdt_disable, NULL, 0);
181 	pr_debug("watchdog disabled\n");
182 
183 	return 0;
184 }
185 
186 static int booke_wdt_set_timeout(struct watchdog_device *wdt_dev,
187 				 unsigned int timeout)
188 {
189 	if (timeout > MAX_WDT_TIMEOUT)
190 		return -EINVAL;
191 	wdt_dev->timeout = timeout;
192 	booke_wdt_set(wdt_dev);
193 
194 	return 0;
195 }
196 
197 static struct watchdog_info booke_wdt_info = {
198 	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
199 	.identity = "PowerPC Book-E Watchdog",
200 };
201 
202 static struct watchdog_ops booke_wdt_ops = {
203 	.owner = THIS_MODULE,
204 	.start = booke_wdt_start,
205 	.stop = booke_wdt_stop,
206 	.ping = booke_wdt_ping,
207 	.set_timeout = booke_wdt_set_timeout,
208 };
209 
210 static struct watchdog_device booke_wdt_dev = {
211 	.info = &booke_wdt_info,
212 	.ops = &booke_wdt_ops,
213 	.min_timeout = 1,
214 	.max_timeout = 0xFFFF
215 };
216 
217 static void __exit booke_wdt_exit(void)
218 {
219 	watchdog_unregister_device(&booke_wdt_dev);
220 }
221 
222 static int __init booke_wdt_init(void)
223 {
224 	int ret = 0;
225 	bool nowayout = WATCHDOG_NOWAYOUT;
226 
227 	pr_info("powerpc book-e watchdog driver loaded\n");
228 	booke_wdt_info.firmware_version = cur_cpu_spec->pvr_value;
229 	booke_wdt_set_timeout(&booke_wdt_dev,
230 			      period_to_sec(booke_wdt_period));
231 	watchdog_set_nowayout(&booke_wdt_dev, nowayout);
232 	if (booke_wdt_enabled)
233 		booke_wdt_start(&booke_wdt_dev);
234 
235 	ret = watchdog_register_device(&booke_wdt_dev);
236 
237 	return ret;
238 }
239 
240 module_init(booke_wdt_init);
241 module_exit(booke_wdt_exit);
242 
243 MODULE_ALIAS("booke_wdt");
244 MODULE_DESCRIPTION("PowerPC Book-E watchdog driver");
245 MODULE_LICENSE("GPL");
246