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

[Stephen Boyd <sboyd@codeaurora.org>]

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.

Cc: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
---

Based on clk-next

 drivers/clk/clk.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index b82714a84f5e..670c8c86ce9f 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1969,16 +1969,18 @@ 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;
-- 
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