avionic design with actual uboot and tooling

submodule of avionic design uboot bootloader and with included tools to
get you started , read readme.md and readme-tk1-loader.md

u-boot/drivers/watchdog/at91sam9_wdt.c

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+/*
+ * [origin: Linux kernel drivers/watchdog/at91sam9_wdt.c]
+ *
+ * Watchdog driver for Atmel AT91SAM9x processors.
+ *
+ * Copyright (C) 2008 Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
+ * Copyright (C) 2008 Renaud CERRATO r.cerrato@til-technologies.fr
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+/*
+ * The Watchdog Timer Mode Register can be only written to once. If the
+ * timeout need to be set from U-Boot, be sure that the bootstrap doesn't
+ * write to this register. Inform Linux to it too
+ */
+
+#include <common.h>
+#include <watchdog.h>
+#include <asm/arch/hardware.h>
+#include <asm/io.h>
+#include <asm/arch/at91_wdt.h>
+
+/*
+ * AT91SAM9 watchdog runs a 12bit counter @ 256Hz,
+ * use this to convert a watchdog
+ * value from/to milliseconds.
+ */
+#define ms_to_ticks(t)	(((t << 8) / 1000) - 1)
+#define ticks_to_ms(t)	(((t + 1) * 1000) >> 8)
+
+/* Hardware timeout in seconds */
+#if !defined(CONFIG_AT91_HW_WDT_TIMEOUT)
+#define WDT_HW_TIMEOUT 2
+#else
+#define WDT_HW_TIMEOUT CONFIG_AT91_HW_WDT_TIMEOUT
+#endif
+
+/*
+ * Set the watchdog time interval in 1/256Hz (write-once)
+ * Counter is 12 bit.
+ */
+static int at91_wdt_settimeout(unsigned int timeout)
+{
+	unsigned int reg;
+	at91_wdt_t *wd = (at91_wdt_t *) ATMEL_BASE_WDT;
+
+	/* Check if disabled */
+	if (readl(&wd->mr) & AT91_WDT_MR_WDDIS) {
+		printf("sorry, watchdog is disabled\n");
+		return -1;
+	}
+
+	/*
+	 * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
+	 *
+	 * Since WDV is a 12-bit counter, the maximum period is
+	 * 4096 / 256 = 16 seconds.
+	 */
+
+	reg = AT91_WDT_MR_WDRSTEN		/* causes watchdog reset */
+		| AT91_WDT_MR_WDDBGHLT		/* disabled in debug mode */
+		| AT91_WDT_MR_WDD(0xfff)	/* restart at any time */
+		| AT91_WDT_MR_WDV(timeout);	/* timer value */
+
+	writel(reg, &wd->mr);
+
+	return 0;
+}
+
+void hw_watchdog_reset(void)
+{
+	at91_wdt_t *wd = (at91_wdt_t *) ATMEL_BASE_WDT;
+	writel(AT91_WDT_CR_WDRSTT | AT91_WDT_CR_KEY, &wd->cr);
+}
+
+void hw_watchdog_init(void)
+{
+	/* 16 seconds timer, resets enabled */
+	at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
+}