drivers/sbsa: add sbsa watchdog driver

Add a driver for configuring the SBSA Generic Watchdog which aids in
the detection of errant system behaviour.

Change-Id: I5a1e7149c69fd8b85be7dfbcf511f431339946f4
Signed-off-by: Aditya Angadi <aditya.angadi@arm.com>

drivers/arm/sbsa/sbsa.c

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2019, ARM Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <plat/common/platform.h>
+#include <drivers/arm/sbsa.h>
+#include <lib/mmio.h>
+#include <stdint_.h>
+#include <assert.h>
+
+void sbsa_watchdog_offset_reg_write(uintptr_t base, uint64_t value)
+{
+	assert((value >> SBSA_WDOG_WOR_WIDTH) == 0);
+	mmio_write_32(base + SBSA_WDOG_WOR_LOW_OFFSET,
+		 ((uint32_t)value & UINT32_MAX));
+	mmio_write_32(base + SBSA_WDOG_WOR_HIGH_OFFSET, (uint32_t)(value >> 32));
+}
+
+/*
+ * Start the watchdog timer at base address "base" for a
+ * period of "ms" milliseconds.The watchdog has to be
+ * refreshed within this time period.
+ */
+void sbsa_wdog_start(uintptr_t base, uint64_t ms)
+{
+	uint64_t counter_freq;
+	uint64_t offset_reg_value;
+
+	counter_freq = (uint64_t)plat_get_syscnt_freq2();
+	offset_reg_value = ms * counter_freq / 1000;
+
+	sbsa_watchdog_offset_reg_write(base, offset_reg_value);
+	mmio_write_32(base + SBSA_WDOG_WCS_OFFSET, SBSA_WDOG_WCS_EN);
+}
+
+/* Stop the watchdog */
+void sbsa_wdog_stop(uintptr_t base)
+{
+	mmio_write_32(base + SBSA_WDOG_WCS_OFFSET, (0x0));
+}

include/drivers/arm/sbsa.h

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2019, ARM Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef SBSA_H
+#define SBSA_H
+
+#include <stdint.h>
+
+/* Register Offsets */
+#define SBSA_WDOG_WCS_OFFSET		UL(0x000)
+#define SBSA_WDOG_WOR_LOW_OFFSET	UL(0x008)
+#define SBSA_WDOG_WOR_HIGH_OFFSET	UL(0x00C)
+
+#define SBSA_WDOG_WCS_EN		U(0x1)
+
+#define SBSA_WDOG_WOR_WIDTH		UL(48)
+
+void sbsa_wdog_start(uintptr_t base, uint64_t ms);
+void sbsa_wdog_stop(uintptr_t base);
+
+#endif /* SBSA_H */