clk: Add clk_parent entry in debugfs

This allows to easily determine the parent in shell scripts without
parsing more complex files.

Add the clk_parent file for all clks which can have a parent, not just
muxes. This way it can be used to determine the clk tree structure
without parsing more complex files.
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/clk.c

@@ -3011,6 +3011,17 @@ static int possible_parents_show(struct seq_file *s, void *data)
 }
 DEFINE_SHOW_ATTRIBUTE(possible_parents);
 
+static int current_parent_show(struct seq_file *s, void *data)
+{
+	struct clk_core *core = s->private;
+
+	if (core->parent)
+		seq_printf(s, "%s\n", core->parent->name);
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(current_parent);
+
 static int clk_duty_cycle_show(struct seq_file *s, void *data)
 {
 	struct clk_core *core = s->private;
@@ -3043,6 +3054,10 @@ static void clk_debug_create_one(struct clk_core *core, struct dentry *pdentry)
 	debugfs_create_file("clk_duty_cycle", 0444, root, core,
 			    &clk_duty_cycle_fops);
 
+	if (core->num_parents > 0)
+		debugfs_create_file("clk_parent", 0444, root, core,
+				    &current_parent_fops);
+
 	if (core->num_parents > 1)
 		debugfs_create_file("clk_possible_parents", 0444, root, core,
 				    &possible_parents_fops);