clk: tegra: Add subtree change notifications

Added PRE_SUBTREE_CHANGE and POST_SUBTREE_CHANGE that called before
and after rate change is propagated down the sub-tree rooted in clk.
This would allow children to be aware that next set rate operation
is triggered by downward rate propagation, rather than direct set rate
on a child clock.

Bug 200267979

Change-Id: I6f2acbeca7cead0ecd385dcb2e58ced32448e998
Signed-off-by: Alex Frid <afrid@nvidia.com>
Signed-off-by: Peter De Schrijver <pdeschrijver@nvidia.com>
(cherry picked from commit 62f0d763fcb6c9d5bd9a373d22d802503ab0fdc5)
Reviewed-on: https://git-master.nvidia.com/r/1558143
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Timo Alho <talho@nvidia.com>

drivers/clk/clk.c

@@ -2554,6 +2554,13 @@ static void clk_change_rate(struct clk_core *core)
 	if (core->ops->post_rate_change)
 		core->ops->post_rate_change(core->hw, old_rate, core->rate);
 
+	/*
+	 * Allow children to be aware that next set rate operation is triggered
+	 * by downward rate propagation, rather than direct set rate on itself.
+	 */
+	if (core->notifier_count)
+		__clk_notify(core, PRE_SUBTREE_CHANGE, old_rate, core->rate);
+
 	/*
 	 * Use safe iteration, as change_rate can actually swap parents
 	 * for certain clock types.
@@ -2569,6 +2576,9 @@ static void clk_change_rate(struct clk_core *core)
 	if (core->new_child)
 		clk_change_rate(core->new_child);
 
+	if (core->notifier_count)
+		__clk_notify(core, POST_SUBTREE_CHANGE, old_rate, core->rate);
+
 	clk_pm_runtime_put(core);
 }
 

include/linux/clk.h

@@ -35,10 +35,19 @@ struct of_phandle_args;
  * POST_RATE_CHANGE - called after the clk rate change has successfully
  *     completed.  Callbacks must always return NOTIFY_DONE or NOTIFY_OK.
  *
+ * PRE_SUBTREE_UPDATE - called before rate change is propagated down to
+ *     sub-tree rooted in clk. Callbacks must always return NOTIFY_DONE
+ *     or NOTIFY_OK.
+ *
+ * POST_SUBTREE_UPDATE - called after rate change is propagated down to
+ *     sub-tree rooted in clk. Callbacks must always return NOTIFY_DONE
+ *     or NOTIFY_OK.
  */
 #define PRE_RATE_CHANGE			BIT(0)
 #define POST_RATE_CHANGE		BIT(1)
 #define ABORT_RATE_CHANGE		BIT(2)
+#define PRE_SUBTREE_CHANGE		BIT(3)
+#define POST_SUBTREE_CHANGE		BIT(4)
 
 /**
  * struct clk_notifier - associate a clk with a notifier