davinci: support re-parenting a clock in the clock framework

The clk_set_parent() API is implemented to enable re-parenting
clocks in the clock tree.

This is useful in DVFS and helps by shifting clocks to an asynchronous
domain where supported by hardware

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>

arch/arm/mach-davinci/clock.c

@@ -141,6 +141,33 @@ int clk_set_rate(struct clk *clk, unsigned long rate)
 }
 EXPORT_SYMBOL(clk_set_rate);
 
+int clk_set_parent(struct clk *clk, struct clk *parent)
+{
+	unsigned long flags;
+
+	if (clk == NULL || IS_ERR(clk))
+		return -EINVAL;
+
+	/* Cannot change parent on enabled clock */
+	if (WARN_ON(clk->usecount))
+		return -EINVAL;
+
+	mutex_lock(&clocks_mutex);
+	clk->parent = parent;
+	list_del_init(&clk->childnode);
+	list_add(&clk->childnode, &clk->parent->children);
+	mutex_unlock(&clocks_mutex);
+
+	spin_lock_irqsave(&clockfw_lock, flags);
+	if (clk->recalc)
+		clk->rate = clk->recalc(clk);
+	propagate_rate(clk);
+	spin_unlock_irqrestore(&clockfw_lock, flags);
+
+	return 0;
+}
+EXPORT_SYMBOL(clk_set_parent);
+
 int clk_register(struct clk *clk)
 {
 	if (clk == NULL || IS_ERR(clk))