MIPS: ralink: adds clkdev code

These SoCs have a limited number of fixed rate clocks. Add support for the
clk and clkdev api.
Signed-off-by: NJohn Crispin <blogic@openwrt.org>
Signed-off-by: NGabor Juhos <juhosg@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/4894/

arch/mips/ralink/clk.c

+/*
+ *  This program is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 2 as published
+ *  by the Free Software Foundation.
+ *
+ *  Copyright (C) 2011 Gabor Juhos <juhosg@openwrt.org>
+ *  Copyright (C) 2013 John Crispin <blogic@openwrt.org>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/clkdev.h>
+#include <linux/clk.h>
+
+#include <asm/time.h>
+
+#include "common.h"
+
+struct clk {
+	struct clk_lookup cl;
+	unsigned long rate;
+};
+
+void ralink_clk_add(const char *dev, unsigned long rate)
+{
+	struct clk *clk = kzalloc(sizeof(struct clk), GFP_KERNEL);
+
+	if (!clk)
+		panic("failed to add clock\n");
+
+	clk->cl.dev_id = dev;
+	clk->cl.clk = clk;
+
+	clk->rate = rate;
+
+	clkdev_add(&clk->cl);
+}
+
+/*
+ * Linux clock API
+ */
+int clk_enable(struct clk *clk)
+{
+	return 0;
+}
+EXPORT_SYMBOL_GPL(clk_enable);
+
+void clk_disable(struct clk *clk)
+{
+}
+EXPORT_SYMBOL_GPL(clk_disable);
+
+unsigned long clk_get_rate(struct clk *clk)
+{
+	return clk->rate;
+}
+EXPORT_SYMBOL_GPL(clk_get_rate);
+
+void __init plat_time_init(void)
+{
+	struct clk *clk;
+
+	ralink_of_remap();
+
+	ralink_clk_init();
+	clk = clk_get_sys("cpu", NULL);
+	if (IS_ERR(clk))
+		panic("unable to get CPU clock, err=%ld", PTR_ERR(clk));
+	pr_info("CPU Clock: %ldMHz\n", clk_get_rate(clk) / 1000000);
+	mips_hpt_frequency = clk_get_rate(clk) / 2;
+	clk_put(clk);
+}