2 * [origin: Linux kernel drivers/watchdog/at91sam9_wdt.c]
4 * Watchdog driver for Atmel AT91SAM9x processors.
6 * Copyright (C) 2008 Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
7 * Copyright (C) 2008 Renaud CERRATO r.cerrato@til-technologies.fr
9 * SPDX-License-Identifier: GPL-2.0+
13 * The Watchdog Timer Mode Register can be only written to once. If the
14 * timeout need to be set from U-Boot, be sure that the bootstrap doesn't
15 * write to this register. Inform Linux to it too
20 #include <asm/arch/hardware.h>
22 #include <asm/arch/at91_wdt.h>
25 * AT91SAM9 watchdog runs a 12bit counter @ 256Hz,
26 * use this to convert a watchdog
27 * value from/to milliseconds.
29 #define ms_to_ticks(t) (((t << 8) / 1000) - 1)
30 #define ticks_to_ms(t) (((t + 1) * 1000) >> 8)
32 /* Hardware timeout in seconds */
33 #define WDT_HW_TIMEOUT 2
36 * Set the watchdog time interval in 1/256Hz (write-once)
39 static int at91_wdt_settimeout(unsigned int timeout)
42 at91_wdt_t *wd = (at91_wdt_t *) ATMEL_BASE_WDT;
44 /* Check if disabled */
45 if (readl(&wd->mr) & AT91_WDT_MR_WDDIS) {
46 printf("sorry, watchdog is disabled\n");
51 * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
53 * Since WDV is a 12-bit counter, the maximum period is
54 * 4096 / 256 = 16 seconds.
57 reg = AT91_WDT_MR_WDRSTEN /* causes watchdog reset */
58 | AT91_WDT_MR_WDDBGHLT /* disabled in debug mode */
59 | AT91_WDT_MR_WDD(0xfff) /* restart at any time */
60 | AT91_WDT_MR_WDV(timeout); /* timer value */
67 void hw_watchdog_reset(void)
69 at91_wdt_t *wd = (at91_wdt_t *) ATMEL_BASE_WDT;
70 writel(AT91_WDT_CR_WDRSTT | AT91_WDT_CR_KEY, &wd->cr);
73 void hw_watchdog_init(void)
75 /* 16 seconds timer, resets enabled */
76 at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));