clk: core: clk_calc_new_rates handles NULL parents

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>

1 files changed, 21 insertions, 8 deletions

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 4daacf5783aa..d83a9e09e1bf 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -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);