clk: fix parent validation in __clk_set_parent()

The below commit introduced a bug in __clk_set_parent()
which could cause it to *skip* the parent validation
which makes sure the parent passed to the api is a valid
one.

    commit 7975059db572eb47f0fb272a62afeae272a4b209
    Author: Rajendra Nayak <rnayak@ti.com>
    Date:   Wed Jun 6 14:41:31 2012 +0530

        clk: Allow late cache allocation for clk->parents

This was identified by the following compiler warning..

    drivers/clk/clk.c: In function '__clk_set_parent':
    drivers/clk/clk.c:1083:5: warning: 'i' may be used uninitialized in this function [-Wuninitialized]

.. as reported by Marc Kleine-Budde.

There were various options discussed on how to fix this, one
being initing 'i' to clk->num_parents, but the below approach
was found to be more appropriate as it also makes the 'parent
validation' code simpler to read.

Reported-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
Cc: stable@kernel.org

1 files changed, 13 insertions, 15 deletions

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index dcbe05616090..9a1eb0cfa95f 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1067,26 +1067,24 @@ static int __clk_set_parent(struct clk *clk, struct clk *parent)
 
         old_parent = clk->parent;
 
-        /* find index of new parent clock using cached parent ptrs */
-        if (clk->parents)
-                for (i = 0; i < clk->num_parents; i++)
-                        if (clk->parents[i] == parent)
-                                break;
-        else
+        if (!clk->parents)
                 clk->parents = kzalloc((sizeof(struct clk*) * clk->num_parents),
                                                                 GFP_KERNEL);
 
         /*
-         * find index of new parent clock using string name comparison
-         * also try to cache the parent to avoid future calls to __clk_lookup
+         * find index of new parent clock using cached parent ptrs,
+         * or if not yet cached, use string name comparison and cache
+         * them now to avoid future calls to __clk_lookup.
          */
-        if (i == clk->num_parents)
-                for (i = 0; i < clk->num_parents; i++)
-                        if (!strcmp(clk->parent_names[i], parent->name)) {
-                                if (clk->parents)
-                                        clk->parents[i] = __clk_lookup(parent->name);
-                                break;
-                        }
+        for (i = 0; i < clk->num_parents; i++) {
+                if (clk->parents && clk->parents[i] == parent)
+                        break;
+                else if (!strcmp(clk->parent_names[i], parent->name)) {
+                        if (clk->parents)
+                                clk->parents[i] = __clk_lookup(parent->name);
+                        break;
+                }
+        }
 
         if (i == clk->num_parents) {
                 pr_debug("%s: clock %s is not a possible parent of clock %s\n",