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    SubjectRe: [PATCH] clk: prevent erronous parsing of children during rate change
    Date
    Quoting Tero Kristo (2014-08-21 06:47:45)
    > 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.
    >
    > Signed-off-by: Tero Kristo <t-kristo@ti.com>
    > To: Mike Turquette <mturquette@linaro.org>
    > Reported-by: Nishanth Menon <nm@ti.com>

    Applied to clk-fixes.

    Thanks!
    Mike

    > ---
    > drivers/clk/clk.c | 7 ++++++-
    > 1 file changed, 6 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
    > index b76fa69..bacc06f 100644
    > --- a/drivers/clk/clk.c
    > +++ b/drivers/clk/clk.c
    > @@ -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;
    > --
    > 1.7.9.5
    >


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