clk: clk_set_parent() with current parent shouldn't fail

If a driver calls clk_set_parent(clk, parent) and parent is the
current parent of clk we shouldn't fail in any case.
Unfortunately if clk is a read-only mux we return -ENOSYS
because we think we can't change the parent, except for in this
special case where we don't actually need to change the parent at
all. Return 0 in such a situation.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Michael Turquette <mturquette@linaro.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 42064cec2364..3e10cdff284b 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -2055,16 +2055,18 @@ static int clk_core_set_parent(struct clk_core *clk, struct clk_core *parent)
         if (!clk)
                 return 0;
 
-        /* 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 */
         clk_prepare_lock();
 
         if (clk->parent == parent)
                 goto out;
 
+        /* verify ops for for multi-parent clks */
+        if ((clk->num_parents > 1) && (!clk->ops->set_parent)) {
+                ret = -ENOSYS;
+                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;