clk: core: clk_calc_new_rates handles NULL parents
Mike Turquette [Mon, 26 Mar 2012 21:45:36 +0000 (14:45 -0700)]
It is possible to call clk_set_rate on a clock with a NULL parent.  One
such example is an adjustable-rate root clock.  Ensure that
clk_calc_new_rates does not dereference parent without checking first
and also handle the corner cases gracefully.

Reported-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

drivers/clk/clk.c

index 4daacf5..d83a9e0 100644 (file)
@@ -763,25 +763,38 @@ static void clk_calc_subtree(struct clk *clk, unsigned long new_rate)
 static struct clk *clk_calc_new_rates(struct clk *clk, unsigned long rate)
 {
        struct clk *top = clk;
-       unsigned long best_parent_rate = clk->parent->rate;
+       unsigned long best_parent_rate;
        unsigned long new_rate;
 
-       if (!clk->ops->round_rate && !(clk->flags & CLK_SET_RATE_PARENT)) {
-               clk->new_rate = clk->rate;
+       /* sanity */
+       if (IS_ERR_OR_NULL(clk))
+               return NULL;
+
+       /* never propagate up to the parent */
+       if (!(clk->flags & CLK_SET_RATE_PARENT)) {
+               if (!clk->ops->round_rate) {
+                       clk->new_rate = clk->rate;
+                       return NULL;
+               } else {
+                       new_rate = clk->ops->round_rate(clk->hw, rate, NULL);
+                       goto out;
+               }
+       }
+
+       /* need clk->parent from here on out */
+       if (!clk->parent) {
+               pr_debug("%s: %s has NULL parent\n", __func__, clk->name);
                return NULL;
        }
 
-       if (!clk->ops->round_rate && (clk->flags & CLK_SET_RATE_PARENT)) {
+       if (!clk->ops->round_rate) {
                top = clk_calc_new_rates(clk->parent, rate);
                new_rate = clk->new_rate = clk->parent->new_rate;
 
                goto out;
        }
 
-       if (clk->flags & CLK_SET_RATE_PARENT)
-               new_rate = clk->ops->round_rate(clk->hw, rate, &best_parent_rate);
-       else
-               new_rate = clk->ops->round_rate(clk->hw, rate, NULL);
+       new_rate = clk->ops->round_rate(clk->hw, rate, &best_parent_rate);
 
        if (best_parent_rate != clk->parent->rate) {
                top = clk_calc_new_rates(clk->parent, best_parent_rate);