dm: implement a Timer uclass

Implement a Timer uclass to work with lib/time.c.

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Acked-by: Simon Glass <sjg@chromium.org>

drivers/timer/timer-uclass.c

@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2015 Thomas Chou <thomas@wytron.com.tw>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <timer.h>
+
+/*
+ * Implement a Timer uclass to work with lib/time.c. The timer is usually
+ * a 32 bits free-running up counter. The get_rate() method is used to get
+ * the input clock frequency of the timer. The get_count() method is used
+ * get the current 32 bits count value. If the hardware is counting down,
+ * the value should be inversed inside the method. There may be no real
+ * tick, and no timer interrupt.
+ */
+
+int timer_get_count(struct udevice *dev, unsigned long *count)
+{
+	const struct timer_ops *ops = device_get_ops(dev);
+
+	if (!ops->get_count)
+		return -ENOSYS;
+
+	return ops->get_count(dev, count);
+}
+
+unsigned long timer_get_rate(struct udevice *dev)
+{
+	struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+
+	return uc_priv->clock_rate;
+}
+
+UCLASS_DRIVER(timer) = {
+	.id		= UCLASS_TIMER,
+	.name		= "timer",
+	.per_device_auto_alloc_size = sizeof(struct timer_dev_priv),
+};