ANDROID: GKI: clk: Add support for clock providers with sync state

Clock providers whose drivers have sync_state() implemented will disable
their clocks once all their consumers have probed. So during
late_initcall_sync(), don't disable unused clocks of these clock
providers.

Also, provide a clk_sync_state() API that clock providers can use to
disable all their unused clocks once they get their sync_state()
callback.

Bug: 144066914
Signed-off-by: Saravana Kannan <saravanak@google.com>
Change-Id: Id01bfc15347812faa19802463c088db162c7d117

drivers/clk/clk.c

@@ -72,6 +72,8 @@ struct clk_core {
 	unsigned long		flags;
 	bool			orphan;
 	bool			rpm_enabled;
+	bool			need_sync;
+	bool			boot_enabled;
 	unsigned int		enable_count;
 	unsigned int		prepare_count;
 	unsigned int		protect_count;
@@ -1300,6 +1302,38 @@ static int clk_disable_unused(void)
 }
 late_initcall_sync(clk_disable_unused);
 
+static void clk_unprepare_disable_dev_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_disable_dev_subtree(child, dev);
+
+	if (core->dev != dev || !core->need_sync)
+		return;
+
+	clk_core_disable_unprepare(core);
+}
+
+void clk_sync_state(struct device *dev)
+{
+	struct clk_core *core;
+
+	clk_prepare_lock();
+
+	hlist_for_each_entry(core, &clk_root_list, child_node)
+		clk_unprepare_disable_dev_subtree(core, dev);
+
+	hlist_for_each_entry(core, &clk_orphan_list, child_node)
+		clk_unprepare_disable_dev_subtree(core, dev);
+
+	clk_prepare_unlock();
+}
+EXPORT_SYMBOL_GPL(clk_sync_state);
+
 static int clk_core_determine_round_nolock(struct clk_core *core,
 					   struct clk_rate_request *req)
 {
@@ -1674,6 +1708,33 @@ static int clk_fetch_parent_index(struct clk_core *core,
 	return i;
 }
 
+static void clk_core_hold_state(struct clk_core *core)
+{
+	if (core->need_sync || !core->boot_enabled)
+		return;
+
+	if (core->orphan || !dev_has_sync_state(core->dev))
+		return;
+
+	if (core->flags & CLK_DONT_HOLD_STATE)
+		return;
+
+	core->need_sync = !clk_core_prepare_enable(core);
+}
+
+static void __clk_core_update_orphan_hold_state(struct clk_core *core)
+{
+	struct clk_core *child;
+
+	if (core->orphan)
+		return;
+
+	clk_core_hold_state(core);
+
+	hlist_for_each_entry(child, &core->children, child_node)
+		__clk_core_update_orphan_hold_state(child);
+}
+
 /*
  * Update the orphan status of @core and all its children.
  */
@@ -3384,6 +3445,8 @@ static int __clk_core_init(struct clk_core *core)
 		rate = 0;
 	core->rate = core->req_rate = rate;
 
+	core->boot_enabled = clk_core_is_enabled(core);
+
 	/*
 	 * Enable CLK_IS_CRITICAL clocks so newly added critical clocks
 	 * don't get accidentally disabled when walking the orphan tree and
@@ -3399,6 +3462,8 @@ static int __clk_core_init(struct clk_core *core)
 		clk_enable_unlock(flags);
 	}
 
+	clk_core_hold_state(core);
+
 	/*
 	 * walk the list of orphan clocks and reparent any that newly finds a
 	 * parent.
@@ -3418,6 +3483,7 @@ static int __clk_core_init(struct clk_core *core)
 			__clk_set_parent_after(orphan, parent, NULL);
 			__clk_recalc_accuracies(orphan);
 			__clk_recalc_rates(orphan, 0);
+			__clk_core_update_orphan_hold_state(orphan);
 		}
 	}
 

include/linux/clk-provider.h

@@ -32,6 +32,7 @@
 #define CLK_OPS_PARENT_ENABLE	BIT(12)
 /* duty cycle call may be forwarded to the parent clock */
 #define CLK_DUTY_CYCLE_PARENT	BIT(13)
+#define CLK_DONT_HOLD_STATE	BIT(14) /* Don't hold state */
 
 struct clk;
 struct clk_hw;
@@ -815,6 +816,7 @@ void devm_clk_unregister(struct device *dev, struct clk *clk);
 
 void clk_hw_unregister(struct clk_hw *hw);
 void devm_clk_hw_unregister(struct device *dev, struct clk_hw *hw);
+void clk_sync_state(struct device *dev);
 
 /* helper functions */
 const char *__clk_get_name(const struct clk *clk);