Commit 067bb174 authored Aug 21, 2014 by Tero Kristo Committed by Mike Turquette Sep 03, 2014

clk: prevent erronous parsing of children during rate change

In some cases, clocks can switch their parent with clk_set_rate, for
example clk_mux can do this in some cases. Current implementation of
clk_change_rate uses un-safe list iteration on the clock children, which
will cause wrong clocks to be parsed in case any of the clock children
change their parents during the change rate operation. Fixed by using
the safe list iterator instead.

The problem was detected due to some divide by zero errors generated
by clock init on dra7-evm board, see discussion under
http://article.gmane.org/gmane.linux.ports.arm.kernel/349180

 for details.

Fixes: 71472c0c ("clk: add support for clock reparent on set_rate")
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Reported-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

parent f4ee3c84

drivers/clk/clk.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -1467,6 +1467,7 @@ static struct clk clk_propagate_rate_change(struct clk clk, unsigned long even
		static void clk_change_rate(struct clk *clk)
		{
		struct clk *child;
		struct hlist_node *tmp;
		unsigned long old_rate;
		unsigned long best_parent_rate = 0;
		bool skip_set_rate = false;
		@@ -1502,7 +1503,11 @@ static void clk_change_rate(struct clk *clk)
		if (clk->notifier_count && old_rate != clk->rate)
		__clk_notify(clk, POST_RATE_CHANGE, old_rate, clk->rate);

		hlist_for_each_entry(child, &clk->children, child_node) {
		/*
		* Use safe iteration, as change_rate can actually swap parents
		* for certain clock types.
		*/
		hlist_for_each_entry_safe(child, tmp, &clk->children, child_node) {
		/* Skip children who will be reparented to another clock */
		if (child->new_parent && child->new_parent != clk)
		continue;

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