1 /*
2  * [origin: Linux kernel drivers/watchdog/at91sam9_wdt.c]
3  *
4  * Watchdog driver for Atmel AT91SAM9x processors.
5  *
6  * Copyright (C) 2008 Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
7  * Copyright (C) 2008 Renaud CERRATO r.cerrato@til-technologies.fr
8  *
9  * This program is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU General Public License
11  * as published by the Free Software Foundation; either version
12  * 2 of the License, or (at your option) any later version.
13  */
14 
15 /*
16  * The Watchdog Timer Mode Register can be only written to once. If the
17  * timeout need to be set from U-Boot, be sure that the bootstrap doesn't
18  * write to this register. Inform Linux to it too
19  */
20 
21 #include <common.h>
22 #include <watchdog.h>
23 #include <asm/arch/hardware.h>
24 #include <asm/io.h>
25 #include <asm/arch/at91_wdt.h>
26 
27 /*
28  * AT91SAM9 watchdog runs a 12bit counter @ 256Hz,
29  * use this to convert a watchdog
30  * value from/to milliseconds.
31  */
32 #define ms_to_ticks(t)	(((t << 8) / 1000) - 1)
33 #define ticks_to_ms(t)	(((t + 1) * 1000) >> 8)
34 
35 /* Hardware timeout in seconds */
36 #define WDT_HW_TIMEOUT 2
37 
38 /*
39  * Set the watchdog time interval in 1/256Hz (write-once)
40  * Counter is 12 bit.
41  */
42 static int at91_wdt_settimeout(unsigned int timeout)
43 {
44 	unsigned int reg;
45 	at91_wdt_t *wd = (at91_wdt_t *) ATMEL_BASE_WDT;
46 
47 	/* Check if disabled */
48 	if (readl(&wd->mr) & AT91_WDT_MR_WDDIS) {
49 		printf("sorry, watchdog is disabled\n");
50 		return -1;
51 	}
52 
53 	/*
54 	 * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
55 	 *
56 	 * Since WDV is a 12-bit counter, the maximum period is
57 	 * 4096 / 256 = 16 seconds.
58 	 */
59 
60 	reg = AT91_WDT_MR_WDRSTEN		/* causes watchdog reset */
61 		| AT91_WDT_MR_WDDBGHLT		/* disabled in debug mode */
62 		| AT91_WDT_MR_WDD(0xfff)	/* restart at any time */
63 		| AT91_WDT_MR_WDV(timeout);	/* timer value */
64 
65 	writel(reg, &wd->mr);
66 
67 	return 0;
68 }
69 
70 void hw_watchdog_reset(void)
71 {
72 	at91_wdt_t *wd = (at91_wdt_t *) ATMEL_BASE_WDT;
73 	writel(AT91_WDT_CR_WDRSTT | AT91_WDT_CR_KEY, &wd->cr);
74 }
75 
76 void hw_watchdog_init(void)
77 {
78 	/* 16 seconds timer, resets enabled */
79 	at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
80 }
81