clk: Fixup errorhandling for clk_set_parent

Fixup the broken feature of allowing reparent of a clk to the
orhpan list and vice verse. When operating on a single-parent
clk, the .set_parent callback for the clk hw is optional to
implement, but for a multi-parent clk it is mandatory.

Moreover improve the errorhandling by verifying the prerequisites
before triggering clk notifiers. This will prevent unnecessary
rollback with ABORT_RATE_CHANGE.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Rajagopal Venkat <rajagopal.venkat@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

1 files changed, 36 insertions, 20 deletions

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 013a3c7fea5b..c83e8e543bab 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1332,15 +1332,10 @@ void __clk_reparent(struct clk *clk, struct clk *new_parent)
         __clk_recalc_rates(clk, POST_RATE_CHANGE);
 }
 
-static int __clk_set_parent(struct clk *clk, struct clk *parent)
+static u8 clk_fetch_parent_index(struct clk *clk, struct clk *parent)
 {
-        struct clk *old_parent;
-        unsigned long flags;
-        int ret = -EINVAL;
         u8 i;
 
-        old_parent = clk->parent;
-
         if (!clk->parents)
                 clk->parents = kzalloc((sizeof(struct clk*) * clk->num_parents),
                                                                 GFP_KERNEL);
@@ -1360,11 +1355,14 @@ static int __clk_set_parent(struct clk *clk, struct clk *parent)
                 }
         }
 
-        if (i == clk->num_parents) {
-                pr_debug("%s: clock %s is not a possible parent of clock %s\n",
-                                __func__, parent->name, clk->name);
-                goto out;
-        }
+        return i;
+}
+
+static int __clk_set_parent(struct clk *clk, struct clk *parent, u8 p_index)
+{
+        unsigned long flags;
+        int ret = 0;
+        struct clk *old_parent = clk->parent;
 
         /* migrate prepare and enable */
         if (clk->prepare_count)
@@ -1377,7 +1375,8 @@ static int __clk_set_parent(struct clk *clk, struct clk *parent)
         clk_enable_unlock(flags);
 
         /* change clock input source */
-        ret = clk->ops->set_parent(clk->hw, i);
+        if (parent && clk->ops->set_parent)
+                ret = clk->ops->set_parent(clk->hw, p_index);
 
         /* clean up old prepare and enable */
         flags = clk_enable_lock();
@@ -1388,7 +1387,6 @@ static int __clk_set_parent(struct clk *clk, struct clk *parent)
         if (clk->prepare_count)
                 __clk_unprepare(old_parent);
 
-out:
         return ret;
 }
 
@@ -1407,11 +1405,14 @@ out:
 int clk_set_parent(struct clk *clk, struct clk *parent)
 {
         int ret = 0;
+        u8 p_index = 0;
+        unsigned long p_rate = 0;
 
         if (!clk || !clk->ops)
                 return -EINVAL;
 
-        if (!clk->ops->set_parent)
+        /* verify ops for for multi-parent clks */
+        if ((clk->num_parents > 1) && (!clk->ops->set_parent))
                 return -ENOSYS;
 
         /* prevent racing with updates to the clock topology */
@@ -1420,19 +1421,34 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
         if (clk->parent == parent)
                 goto out;
 
+        /* check that we are allowed to re-parent if the clock is in use */
+        if ((clk->flags & CLK_SET_PARENT_GATE) && clk->prepare_count) {
+                ret = -EBUSY;
+                goto out;
+        }
+
+        /* try finding the new parent index */
+        if (parent) {
+                p_index = clk_fetch_parent_index(clk, parent);
+                p_rate = parent->rate;
+                if (p_index == clk->num_parents) {
+                        pr_debug("%s: clk %s can not be parent of clk %s\n",
+                                        __func__, parent->name, clk->name);
+                        ret = -EINVAL;
+                        goto out;
+                }
+        }
+
         /* propagate PRE_RATE_CHANGE notifications */
         if (clk->notifier_count)
-                ret = __clk_speculate_rates(clk, parent->rate);
+                ret = __clk_speculate_rates(clk, p_rate);
 
         /* abort if a driver objects */
         if (ret == NOTIFY_STOP)
                 goto out;
 
-        /* only re-parent if the clock is not in use */
-        if ((clk->flags & CLK_SET_PARENT_GATE) && clk->prepare_count)
-                ret = -EBUSY;
-        else
-                ret = __clk_set_parent(clk, parent);
+        /* do the re-parent */
+        ret = __clk_set_parent(clk, parent, p_index);
 
         /* propagate ABORT_RATE_CHANGE if .set_parent failed */
         if (ret) {