1 files changed, 82 insertions, 0 deletions
diff --git a/drivers/delay_timer/delay_timer.c b/drivers/delay_timer/delay_timer.c
new file mode 100644
index 0000000..a3fd7bf
--- /dev/null
+++ b/drivers/delay_timer/delay_timer.c
@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <assert.h>
+
+#include <platform_def.h>
+
+#include <drivers/delay_timer.h>
+#include <lib/utils_def.h>
+
+/***********************************************************
+ * The delay timer implementation
+ ***********************************************************/
+static const timer_ops_t *timer_ops;
+
+/***********************************************************
+ * Delay for the given number of microseconds. The driver must
+ * be initialized before calling this function.
+ ***********************************************************/
+void udelay(uint32_t usec)
+{
+	assert((timer_ops != NULL) &&
+		(timer_ops->clk_mult != 0U) &&
+		(timer_ops->clk_div != 0U) &&
+		(timer_ops->get_timer_value != NULL));
+
+	uint32_t start, delta;
+	uint64_t total_delta;
+
+	assert(usec < (UINT64_MAX / timer_ops->clk_div));
+
+	start = timer_ops->get_timer_value();
+
+	/* Add an extra tick to avoid delaying less than requested. */
+	total_delta =
+		div_round_up((uint64_t)usec * timer_ops->clk_div,
+						timer_ops->clk_mult) + 1U;
+	/*
+	 * Precaution for the total_delta ~ UINT32_MAX and the fact that we
+	 * cannot catch every tick of the timer.
+	 * For example 100MHz timer over 25MHz APB will miss at least 4 ticks.
+	 * 1000U is an arbitrary big number which is believed to be sufficient.
+	 */
+	assert(total_delta < (UINT32_MAX - 1000U));
+
+	do {
+		/*
+		 * If the timer value wraps around, the subtraction will
+		 * overflow and it will still give the correct result.
+		 * delta is decreasing counter
+		 */
+		delta = start - timer_ops->get_timer_value();
+
+	} while (delta < total_delta);
+}
+
+/***********************************************************
+ * Delay for the given number of milliseconds. The driver must
+ * be initialized before calling this function.
+ ***********************************************************/
+void mdelay(uint32_t msec)
+{
+	assert((msec * 1000UL) < UINT32_MAX);
+	udelay(msec * 1000U);
+}
+
+/***********************************************************
+ * Initialize the timer. The fields in the provided timer
+ * ops pointer must be valid.
+ ***********************************************************/
+void timer_init(const timer_ops_t *ops_ptr)
+{
+	assert((ops_ptr != NULL)  &&
+		(ops_ptr->clk_mult != 0U) &&
+		(ops_ptr->clk_div != 0U) &&
+		(ops_ptr->get_timer_value != NULL));
+
+	timer_ops = ops_ptr;
+}