davinci: enable easy top down traversal of clock tree

Achieve easy top down traversal of clock tree by keeping
track of each clock's list of children.

This is useful in supporting DVFS where clock rates of
all children need to be updated in an efficient manner.

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

arch/arm/mach-davinci/clock.c

@@ -123,8 +123,12 @@ int clk_register(struct clk *clk)
 			clk->name, clk->parent->name))
 		return -EINVAL;
 
+	INIT_LIST_HEAD(&clk->children);
+
 	mutex_lock(&clocks_mutex);
 	list_add_tail(&clk->node, &clocks);
+	if (clk->parent)
+		list_add_tail(&clk->childnode, &clk->parent->children);
 	mutex_unlock(&clocks_mutex);
 
 	/* If rate is already set, use it */
@@ -146,6 +150,7 @@ void clk_unregister(struct clk *clk)
 
 	mutex_lock(&clocks_mutex);
 	list_del(&clk->node);
+	list_del(&clk->childnode);
 	mutex_unlock(&clocks_mutex);
 }
 EXPORT_SYMBOL(clk_unregister);
@@ -352,8 +357,7 @@ dump_clock(struct seq_file *s, unsigned nest, struct clk *parent)
 	/* REVISIT show device associations too */
 
 	/* cost is now small, but not linear... */
-	list_for_each_entry(clk, &clocks, node) {
-		if (clk->parent == parent)
+	list_for_each_entry(clk, &parent->children, childnode) {
 		dump_clock(s, nest + NEST_DELTA, clk);
 	}
 }

arch/arm/mach-davinci/clock.h

@@ -69,6 +69,8 @@ struct clk {
 	u8			lpsc;
 	u8			psc_ctlr;
 	struct clk              *parent;
+	struct list_head	children; 	/* list of children */
+	struct list_head	childnode;	/* parent's child list node */
 	struct pll_data         *pll_data;
 	u32                     div_reg;
 };