sh: clkfwk: Improve the generic clk_set_parent() implementation.

This causes the generic clk_set_parent() implementation to be a bit more
intelligent. A clk_reparent() is added to move the clock over to the new
parent's sibling list, which then allows the generic rate propagation
code to succeed. This also becomes a nop if the new and old parents are
unchanged.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/include/asm/clock.h

@@ -48,6 +48,7 @@ int clk_init(void);
 unsigned long followparent_recalc(struct clk *);
 void recalculate_root_clocks(void);
 void propagate_rate(struct clk *);
+int clk_reparent(struct clk *child, struct clk *parent);
 void clk_recalc_rate(struct clk *);
 int clk_register(struct clk *);
 void clk_unregister(struct clk *);

arch/sh/kernel/cpu/clock.c

@@ -81,6 +81,19 @@ unsigned long followparent_recalc(struct clk *clk)
 	return clk->parent->rate;
 }
 
+int clk_reparent(struct clk *child, struct clk *parent)
+{
+	list_del_init(&child->sibling);
+	if (parent)
+		list_add(&child->sibling, &parent->children);
+	child->parent = parent;
+
+	/* now do the debugfs renaming to reattach the child
+	   to the proper parent */
+
+	return 0;
+}
+
 /* Propagate rate to children */
 void propagate_rate(struct clk *tclk)
 {
@@ -288,12 +301,19 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
 
 	if (!parent || !clk)
 		return ret;
+	if (clk->parent == parent)
+		return 0;
 
 	spin_lock_irqsave(&clock_lock, flags);
 	if (clk->usecount == 0) {
 		if (clk->ops->set_parent)
 			ret = clk->ops->set_parent(clk, parent);
+		else
+			ret = clk_reparent(clk, parent);
+
 		if (ret == 0) {
+			pr_debug("clock: set parent of %s to %s (new rate %ld)\n",
+				 clk->name, clk->parent->name, clk->rate);
 			if (clk->ops->recalc)
 				clk->rate = clk->ops->recalc(clk);
 			propagate_rate(clk);