[PATCH v2] clk: Add clk_parent entry in debugfs

[Leonard Crestez <leonard.crestez@nxp.com>]

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>

---
Changes since v1: Only add clk_parent if num_parents > 0

It seems that num_parents is only initialized once and never changes so
having a check here makes sense: skip the clk_parent file if the clk can
never have parent (num_parent == 0) but keep it if the parent is
constant (num_parents == 1).

It seems the parent can be set to NULL later so keep the check for
(core->parent != NULL) in the show function.

Link to v1: https://patchwork.kernel.org/patch/10959347/
---
 drivers/clk/clk.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index aa51756fd4d6..d21a219deef8 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3009,10 +3009,21 @@ static int possible_parents_show(struct seq_file *s, void *data)
 
 	return 0;
 }
 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;
 	struct clk_duty *duty = &core->duty;
 
@@ -3041,10 +3052,14 @@ static void clk_debug_create_one(struct clk_core *core, struct dentry *pdentry)
 	debugfs_create_u32("clk_protect_count", 0444, root, &core->protect_count);
 	debugfs_create_u32("clk_notifier_count", 0444, root, &core->notifier_count);
 	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);
 
 	if (core->ops->debug_init)
-- 
2.17.1