[RFC 1/2] clk: Add generic sync_state callback for disabling unused clocks

[Abel Vesa]

There are unused clocks that need to stay enabled on clk_disable_unused,
but rather should be disabled later on on sync_state. Provide a generic
sync_state callback for the clock providers that register such clocks.
Then, use the same mechanism as clk_disable_unused from that generic
callback, but pass the device to make sure only the clocks belonging to
the current clock provider get disabled, if unused. Also, during the
default clk_disable_unused, if the driver that registered the clock has
the generic clk_sync_state_disable_unused callback set for sync_state,
leave its clocks enabled.

Signed-off-by: Abel Vesa <abel.vesa@xxxxxxxxxx>
---
 drivers/clk/clk.c            | 67 +++++++++++++++++++++++++++---------
 include/linux/clk-provider.h |  1 +
 2 files changed, 52 insertions(+), 16 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 7fc191c15507..ea55806505c0 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1218,19 +1218,31 @@ static void clk_core_disable_unprepare(struct clk_core *core)
 	clk_core_unprepare_lock(core);
 }
 
-static void __init clk_unprepare_unused_subtree(struct clk_core *core)
+static void clk_unprepare_unused_subtree(struct clk_core *core,
+						struct device *dev)
 {
 	struct clk_core *child;
 
 	lockdep_assert_held(&prepare_lock);
 
 	hlist_for_each_entry(child, &core->children, child_node)
-		clk_unprepare_unused_subtree(child);
+		clk_unprepare_unused_subtree(child, dev);
+
+	if (dev && core->dev != dev)
+		return;
+
+	/*
+	 * clock will be unprepared on sync_state,
+	 * so leave as is on clk_disable_unused
+	 */
+	if (!dev && dev_has_sync_state(core->dev) &&
+		core->dev->driver->sync_state == clk_sync_state_disable_unused)
+		return;
 
 	if (core->prepare_count)
 		return;
 
-	if (core->flags & CLK_IGNORE_UNUSED)
+	if (!dev && core->flags & CLK_IGNORE_UNUSED)
 		return;
 
 	if (clk_pm_runtime_get(core))
@@ -1248,7 +1260,8 @@ static void __init clk_unprepare_unused_subtree(struct clk_core *core)
 	clk_pm_runtime_put(core);
 }
 
-static void __init clk_disable_unused_subtree(struct clk_core *core)
+static void clk_disable_unused_subtree(struct clk_core *core,
+					struct device *dev)
 {
 	struct clk_core *child;
 	unsigned long flags;
@@ -1256,7 +1269,18 @@ static void __init clk_disable_unused_subtree(struct clk_core *core)
 	lockdep_assert_held(&prepare_lock);
 
 	hlist_for_each_entry(child, &core->children, child_node)
-		clk_disable_unused_subtree(child);
+		clk_disable_unused_subtree(child, dev);
+
+	if (dev && core->dev != dev)
+		return;
+
+	/*
+	 * clock will be disabled on sync_state,
+	 * so leave as is on clk_disable_unused
+	 */
+	if (!dev && dev_has_sync_state(core->dev) &&
+		core->dev->driver->sync_state == clk_sync_state_disable_unused)
+		return;
 
 	if (core->flags & CLK_OPS_PARENT_ENABLE)
 		clk_core_prepare_enable(core->parent);
@@ -1269,7 +1293,7 @@ static void __init clk_disable_unused_subtree(struct clk_core *core)
 	if (core->enable_count)
 		goto unlock_out;
 
-	if (core->flags & CLK_IGNORE_UNUSED)
+	if (!dev && core->flags & CLK_IGNORE_UNUSED)
 		goto unlock_out;
 
 	/*
@@ -1302,35 +1326,46 @@ static int __init clk_ignore_unused_setup(char *__unused)
 }
 __setup("clk_ignore_unused", clk_ignore_unused_setup);
 
-static int __init clk_disable_unused(void)
+static void __clk_disable_unused(struct device *dev)
 {
 	struct clk_core *core;
 
-	if (clk_ignore_unused) {
-		pr_warn("clk: Not disabling unused clocks\n");
-		return 0;
-	}
-
 	clk_prepare_lock();
 
 	hlist_for_each_entry(core, &clk_root_list, child_node)
-		clk_disable_unused_subtree(core);
+		clk_disable_unused_subtree(core, dev);
 
 	hlist_for_each_entry(core, &clk_orphan_list, child_node)
-		clk_disable_unused_subtree(core);
+		clk_disable_unused_subtree(core, dev);
 
 	hlist_for_each_entry(core, &clk_root_list, child_node)
-		clk_unprepare_unused_subtree(core);
+		clk_unprepare_unused_subtree(core, dev);
 
 	hlist_for_each_entry(core, &clk_orphan_list, child_node)
-		clk_unprepare_unused_subtree(core);
+		clk_unprepare_unused_subtree(core, dev);
 
 	clk_prepare_unlock();
+}
+
+static int __init clk_disable_unused(void)
+{
+	if (clk_ignore_unused) {
+		pr_warn("clk: Not disabling unused clocks\n");
+		return 0;
+	}
+
+	__clk_disable_unused(NULL);
 
 	return 0;
 }
 late_initcall_sync(clk_disable_unused);
 
+void clk_sync_state_disable_unused(struct device *dev)
+{
+	__clk_disable_unused(dev);
+}
+EXPORT_SYMBOL_GPL(clk_sync_state_disable_unused);
+
 static int clk_core_determine_round_nolock(struct clk_core *core,
 					   struct clk_rate_request *req)
 {
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 72d937c03a3e..5d3ed2b14f2c 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -679,6 +679,7 @@ struct clk *clk_register_divider_table(struct device *dev, const char *name,
 		void __iomem *reg, u8 shift, u8 width,
 		u8 clk_divider_flags, const struct clk_div_table *table,
 		spinlock_t *lock);
+void clk_sync_state_disable_unused(struct device *dev);
 /**
  * clk_register_divider - register a divider clock with the clock framework
  * @dev: device registering this clock
-- 
2.34.3