[PATCH v5 1/6] clk: add of_clk_get_parent_rate function

[Ray Jui]

Sometimes a clock needs to know the rate of its parent before itself is
registered to the framework. An example is that a PLL may need to
initialize itself to a specific VCO frequency, before registering to the
framework. The parent rate needs to be known, for PLL multipliers and
divisors to be configured properly.

Introduce helper function of_clk_get_parent_rate, which can be used to
obtain the parent rate of a clock, given a device node and index.

Signed-off-by: Ray Jui <rjui@xxxxxxxxxxxx>
---
 drivers/clk/clk.c            |   17 +++++++++++++++++
 include/linux/clk-provider.h |    6 +++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index d48ac71..e1893a2 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -2581,6 +2581,23 @@ const char *of_clk_get_parent_name(struct device_node *np, int index)
 }
 EXPORT_SYMBOL_GPL(of_clk_get_parent_name);
 
+unsigned long of_clk_get_parent_rate(struct device_node *np, int index)
+{
+	const char *parent_name;
+	struct clk *parent_clk;
+
+	parent_name = of_clk_get_parent_name(np, index);
+	if (!parent_name)
+		return 0;
+
+	parent_clk = __clk_lookup(parent_name);
+	if (!parent_clk)
+		return 0;
+
+	return clk_get_rate(parent_clk);
+}
+EXPORT_SYMBOL_GPL(of_clk_get_parent_rate);
+
 struct clock_provider {
 	of_clk_init_cb_t clk_init_cb;
 	struct device_node *np;
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index d936409..e1e2d95 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -585,7 +585,7 @@ struct clk *of_clk_src_simple_get(struct of_phandle_args *clkspec,
 struct clk *of_clk_src_onecell_get(struct of_phandle_args *clkspec, void *data);
 int of_clk_get_parent_count(struct device_node *np);
 const char *of_clk_get_parent_name(struct device_node *np, int index);
-
+unsigned long of_clk_get_parent_rate(struct device_node *np, int index);
 void of_clk_init(const struct of_device_id *matches);
 
 #else /* !CONFIG_OF */
@@ -614,6 +614,10 @@ static inline const char *of_clk_get_parent_name(struct device_node *np,
 {
 	return NULL;
 }
+static unsigned long of_clk_get_parent_rate(struct device_node *np, int index)
+{
+	return 0;
+}
 #define of_clk_init(matches) \
 	{ while (0); }
 #endif /* CONFIG_OF */
-- 
1.7.9.5

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