Add a simple ARM SP805 watchdog driver

Based on SP805 Programmer's model (ARM DDI 0270B). This driver
provides three public APIs:

    void sp805_start(uintptr_t base, unsigned long ticks);
    void sp805_stop(uintptr_t base);
    void sp805_refresh(uintptr_t base, unsigned long ticks);

Upon start, the watchdog starts counting down from the number of
ticks specified. When the count reaches 0 an interrupt is triggered.
The watchdog restarts counting down from the number of ticks
specified. If the count reaches 0 again, the system is reset. A
mechanism to handle the interrupt has not been implemented. Instead,
the API to refresh the watchdog should be used instead to prevent a
system reset.

Change-Id: I799d53f8d1213b10b341a4a67fde6486e89a3dab

drivers/arm/sp805/sp805.c

+/*
+ * Copyright (c) 2015, ARM Limited and Contributors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <mmio.h>
+#include <sp805.h>
+#include <stdint.h>
+
+/* Inline register access functions */
+
+static inline void sp805_write_wdog_load(uintptr_t base, unsigned long value)
+{
+	mmio_write_32(base + SP805_WDOG_LOAD_OFF, value);
+}
+
+static inline void sp805_write_wdog_ctrl(uintptr_t base, unsigned long value)
+{
+	mmio_write_32(base + SP805_WDOG_CTR_OFF, value);
+}
+
+static inline void sp805_write_wdog_lock(uintptr_t base, unsigned long value)
+{
+	mmio_write_32(base + SP805_WDOG_LOCK_OFF, value);
+}
+
+
+/* Public API implementation */
+
+void sp805_start(uintptr_t base, unsigned long ticks)
+{
+	sp805_write_wdog_load(base, ticks);
+	sp805_write_wdog_ctrl(base, SP805_CTR_RESEN | SP805_CTR_INTEN);
+	/* Lock registers access */
+	sp805_write_wdog_lock(base, 0);
+}
+
+void sp805_stop(uintptr_t base)
+{
+	sp805_write_wdog_lock(base, WDOG_UNLOCK_KEY);
+	sp805_write_wdog_ctrl(base, 0);
+}
+
+void sp805_refresh(uintptr_t base, unsigned long ticks)
+{
+	sp805_write_wdog_lock(base, WDOG_UNLOCK_KEY);
+	sp805_write_wdog_load(base, ticks);
+	sp805_write_wdog_lock(base, 0);
+}

include/drivers/arm/sp805.h

+/*
+ * Copyright (c) 2015, ARM Limited and Contributors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef __SP805_H__
+#define __SP805_H__
+
+/* SP805 register offset */
+#define SP805_WDOG_LOAD_OFF		0x000
+#define SP805_WDOG_CTR_OFF		0x008
+#define SP805_WDOG_LOCK_OFF		0xc00
+
+/* Magic word to unlock the wd registers */
+#define WDOG_UNLOCK_KEY			0x1ACCE551
+
+/* Register field definitions */
+#define SP805_CTR_RESEN			(1 << 1)
+#define SP805_CTR_INTEN			(1 << 0)
+
+#ifndef __ASSEMBLY__
+
+#include <stdint.h>
+
+/* Public high level API */
+
+void sp805_start(uintptr_t base, unsigned long ticks);
+void sp805_stop(uintptr_t base);
+void sp805_refresh(uintptr_t base, unsigned long ticks);
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* __SP805_H__ */