clk: Make of_clk_get_parent_name() robust with #clock-cells = 1

If a clock provider has #clock-cells = 1 and we call
of_clk_get_parent_name() on it we may end up returning the name
of the provider node if the provider doesn't have a
clock-output-names property. This doesn't make sense, especially
when you consider that calling of_clk_get_parent_name() on such a
node with different indices will return the same name each time.

Let's try getting the clock from the framework via of_clk_get()
instead, and only fallback to the node name if we have a provider
with #clock-cells = 0. This way, we can't hand out the same name
for different clocks when we don't actually know their names.

Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index b005f666e3a1a7166c7d348ab55405b1c7e5a407..a0fe9ca1f0af964140abe52b093a26f6ec13d4ae 100644 (file)
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3055,6 +3055,7 @@ const char *of_clk_get_parent_name(struct device_node *np, int index)
        u32 pv;
        int rc;
        int count;
+       struct clk *clk;
 
        if (index < 0)
                return NULL;
@@ -3080,8 +3081,25 @@ const char *of_clk_get_parent_name(struct device_node *np, int index)
 
        if (of_property_read_string_index(clkspec.np, "clock-output-names",
                                          index,
-                                         &clk_name) < 0)
-               clk_name = clkspec.np->name;
+                                         &clk_name) < 0) {
+               /*
+                * Best effort to get the name if the clock has been
+                * registered with the framework. If the clock isn't
+                * registered, we return the node name as the name of
+                * the clock as long as #clock-cells = 0.
+                */
+               clk = of_clk_get_from_provider(&clkspec);
+               if (IS_ERR(clk)) {
+                       if (clkspec.args_count == 0)
+                               clk_name = clkspec.np->name;
+                       else
+                               clk_name = NULL;
+               } else {
+                       clk_name = __clk_get_name(clk);
+                       clk_put(clk);
+               }
+       }
+
 
        of_node_put(clkspec.np);
        return clk_name;