clk: Introduce the clk_hw_get_rate_range function

Some clock providers are hand-crafting their clk_rate_request, and need
to figure out the current boundaries of their clk_hw to fill it
properly.

Let's create such a function for clock providers.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220816112530.1837489-24-maxime@cerno.tech
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/clk.c

@@ -684,6 +684,22 @@ static void clk_core_get_boundaries(struct clk_core *core,
 		*max_rate = min(*max_rate, clk_user->max_rate);
 }
 
+/*
+ * clk_hw_get_rate_range() - returns the clock rate range for a hw clk
+ * @hw: the hw clk we want to get the range from
+ * @min_rate: pointer to the variable that will hold the minimum
+ * @max_rate: pointer to the variable that will hold the maximum
+ *
+ * Fills the @min_rate and @max_rate variables with the minimum and
+ * maximum that clock can reach.
+ */
+void clk_hw_get_rate_range(struct clk_hw *hw, unsigned long *min_rate,
+			   unsigned long *max_rate)
+{
+	clk_core_get_boundaries(hw->core, min_rate, max_rate);
+}
+EXPORT_SYMBOL_GPL(clk_hw_get_rate_range);
+
 static bool clk_core_check_boundaries(struct clk_core *core,
 				      unsigned long min_rate,
 				      unsigned long max_rate)

include/linux/clk-provider.h

@@ -1267,6 +1267,8 @@ int clk_mux_determine_rate_flags(struct clk_hw *hw,
 				 struct clk_rate_request *req,
 				 unsigned long flags);
 void clk_hw_reparent(struct clk_hw *hw, struct clk_hw *new_parent);
+void clk_hw_get_rate_range(struct clk_hw *hw, unsigned long *min_rate,
+			   unsigned long *max_rate);
 void clk_hw_set_rate_range(struct clk_hw *hw, unsigned long min_rate,
 			   unsigned long max_rate);