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* [PATCH v2] clk: walk orphan list on clock provider registration
@ 2019-12-03  8:08 Jerome Brunet
  2019-12-13  2:54 ` Stephen Boyd
  0 siblings, 1 reply; 2+ messages in thread
From: Jerome Brunet @ 2019-12-03  8:08 UTC (permalink / raw)
  To: Stephen Boyd, Michael Turquette
  Cc: Jerome Brunet, Kevin Hilman, linux-amlogic, linux-kernel,
	linux-clk, Jian Hu

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.

Reported-by: Jian Hu <jian.hu@amlogic.com>
Fixes: fc0c209c147f ("clk: Allow parents to be specified without string names")
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
---
 drivers/clk/clk.c | 62 ++++++++++++++++++++++++++++++-----------------
 1 file changed, 40 insertions(+), 22 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index ef4416721777..df16a535e800 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3249,6 +3249,41 @@ static inline void clk_debug_unregister(struct clk_core *core)
 }
 #endif
 
+static void clk_core_reparent_orphans_nolock(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);
+		}
+	}
+}
+
+static void clk_core_reparent_orphans(void)
+{
+	clk_prepare_lock();
+	clk_core_reparent_orphans_nolock();
+	clk_prepare_unlock();
+}
+
 /**
  * __clk_core_init - initialize the data structures in a struct clk_core
  * @core:	clk_core being initialized
@@ -3259,8 +3294,6 @@ 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 +3449,8 @@ 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_orphans_nolock();
 
-		/*
-		 * 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 +4302,8 @@ int of_clk_add_provider(struct device_node *np,
 	mutex_unlock(&of_clk_mutex);
 	pr_debug("Added clock from %pOF\n", np);
 
+	clk_core_reparent_orphans();
+
 	ret = of_clk_set_defaults(np, true);
 	if (ret < 0)
 		of_clk_del_provider(np);
@@ -4323,6 +4339,8 @@ 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_core_reparent_orphans();
+
 	ret = of_clk_set_defaults(np, true);
 	if (ret < 0)
 		of_clk_del_provider(np);
-- 
2.23.0


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH v2] clk: walk orphan list on clock provider registration
  2019-12-03  8:08 [PATCH v2] clk: walk orphan list on clock provider registration Jerome Brunet
@ 2019-12-13  2:54 ` Stephen Boyd
  0 siblings, 0 replies; 2+ messages in thread
From: Stephen Boyd @ 2019-12-13  2:54 UTC (permalink / raw)
  To: Jerome Brunet, Michael Turquette
  Cc: Jerome Brunet, Kevin Hilman, linux-amlogic, linux-kernel,
	linux-clk, Jian Hu

Quoting Jerome Brunet (2019-12-03 00:08:05)
> 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.
> 
> Reported-by: Jian Hu <jian.hu@amlogic.com>
> Fixes: fc0c209c147f ("clk: Allow parents to be specified without string names")
> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
> ---

Applied to clk-fixes


^ permalink raw reply	[flat|nested] 2+ messages in thread

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