linux-kernel - [PATCH] clk: walk orphan list on clock provider registration

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Date:   Fri, 29 Nov 2019 17:16:58 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>
Cc:     Jerome Brunet <jbrunet@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org
Subject: [PATCH] clk: walk orphan list on clock provider registration

So far, we walked the orphan list every time a new clock was registered
in CCF. This was fine since the clocks were only referenced by name.

Now that the clock can be referenced through DT, it is not enough:
* Controller A register first a reference clocks from controller B
  through DT.
* Controller B register all its clocks then register the provider.

Each time controller B registers a new clock, the orphan list is walked
but it can't match since the provider is registered yet. When the
provider is finally registered, the orphan list is not walked unless
another clock is registered afterward.

This can lead to situation where some clocks remain orphaned even if
the parent is available.

Walking the orphan list on provider registration solves the problem.

Fixes: fc0c209c147f ("clk: Allow parents to be specified without string names")
Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
---
 drivers/clk/clk.c | 59 +++++++++++++++++++++++++++++------------------
 1 file changed, 37 insertions(+), 22 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index ef4416721777..917ba37c3b9d 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3249,6 +3249,34 @@ static inline void clk_debug_unregister(struct clk_core *core)
 }
 #endif
 
+static void __clk_core_reparent_orphan(void)
+{
+	struct clk_core *orphan;
+	struct hlist_node *tmp2;
+
+	/*
+	 * walk the list of orphan clocks and reparent any that newly finds a
+	 * parent.
+	 */
+	hlist_for_each_entry_safe(orphan, tmp2, &clk_orphan_list, child_node) {
+		struct clk_core *parent = __clk_init_parent(orphan);
+
+		/*
+		 * We need to use __clk_set_parent_before() and _after() to
+		 * to properly migrate any prepare/enable count of the orphan
+		 * clock. This is important for CLK_IS_CRITICAL clocks, which
+		 * are enabled during init but might not have a parent yet.
+		 */
+		if (parent) {
+			/* update the clk tree topology */
+			__clk_set_parent_before(orphan, parent);
+			__clk_set_parent_after(orphan, parent, NULL);
+			__clk_recalc_accuracies(orphan);
+			__clk_recalc_rates(orphan, 0);
+		}
+	}
+}
+
 /**
  * __clk_core_init - initialize the data structures in a struct clk_core
  * @core:	clk_core being initialized
@@ -3259,8 +3287,6 @@ static inline void clk_debug_unregister(struct clk_core *core)
 static int __clk_core_init(struct clk_core *core)
 {
 	int ret;
-	struct clk_core *orphan;
-	struct hlist_node *tmp2;
 	unsigned long rate;
 
 	if (!core)
@@ -3416,27 +3442,8 @@ static int __clk_core_init(struct clk_core *core)
 		clk_enable_unlock(flags);
 	}
 
-	/*
-	 * walk the list of orphan clocks and reparent any that newly finds a
-	 * parent.
-	 */
-	hlist_for_each_entry_safe(orphan, tmp2, &clk_orphan_list, child_node) {
-		struct clk_core *parent = __clk_init_parent(orphan);
+	__clk_core_reparent_orphan();
 
-		/*
-		 * We need to use __clk_set_parent_before() and _after() to
-		 * to properly migrate any prepare/enable count of the orphan
-		 * clock. This is important for CLK_IS_CRITICAL clocks, which
-		 * are enabled during init but might not have a parent yet.
-		 */
-		if (parent) {
-			/* update the clk tree topology */
-			__clk_set_parent_before(orphan, parent);
-			__clk_set_parent_after(orphan, parent, NULL);
-			__clk_recalc_accuracies(orphan);
-			__clk_recalc_rates(orphan, 0);
-		}
-	}
 
 	kref_init(&core->ref);
 out:
@@ -4288,6 +4295,10 @@ int of_clk_add_provider(struct device_node *np,
 	mutex_unlock(&of_clk_mutex);
 	pr_debug("Added clock from %pOF\n", np);
 
+	clk_prepare_lock();
+	__clk_core_reparent_orphan();
+	clk_prepare_unlock();
+
 	ret = of_clk_set_defaults(np, true);
 	if (ret < 0)
 		of_clk_del_provider(np);
@@ -4323,6 +4334,10 @@ int of_clk_add_hw_provider(struct device_node *np,
 	mutex_unlock(&of_clk_mutex);
 	pr_debug("Added clk_hw provider from %pOF\n", np);
 
+	clk_prepare_lock();
+	__clk_core_reparent_orphan();
+	clk_prepare_unlock();
+
 	ret = of_clk_set_defaults(np, true);
 	if (ret < 0)
 		of_clk_del_provider(np);
-- 
2.23.0