clk: at91: Add clock driver

The patch is referred to at91 clock driver of Linux, to make
the clock node descriptions in DT aligned with the Linux's.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/clk/at91/clk-master.c b/drivers/clk/at91/clk-master.c
new file mode 100644
index 0000000..284b248
--- /dev/null
+++ b/drivers/clk/at91/clk-master.c
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2016 Atmel Corporation
+ *               Wenyou.Yang <wenyou.yang@atmel.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <clk-uclass.h>
+#include <dm/device.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+static ulong at91_master_clk_get_rate(struct clk *clk)
+{
+	return gd->arch.mck_rate_hz;
+}
+
+static struct clk_ops at91_master_clk_ops = {
+	.get_rate = at91_master_clk_get_rate,
+};
+
+static const struct udevice_id at91_master_clk_match[] = {
+	{ .compatible = "atmel,at91sam9x5-clk-master" },
+	{}
+};
+
+U_BOOT_DRIVER(at91_master_clk) = {
+	.name = "at91-master-clk",
+	.id = UCLASS_CLK,
+	.of_match = at91_master_clk_match,
+	.ops = &at91_master_clk_ops,
+};