clk: qcom: clk-rcg2: add rcg2 mux ops

An RCG may act as a mux that switch between 2 parents.
This is the case on IPQ6018 and IPQ8074 where the APCS core clk that feeds
the CPU cluster clock just switches between XO and the PLL that feeds it.

Add the required ops to add support for this special configuration and use
the generic mux function to determine the rate.

This way we dont have to keep a essentially dummy frequency table to use
RCG2 as a mux.
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Signed-off-by: Robert Marko <robimarko@gmail.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220818220628.339366-1-robimarko@gmail.com

drivers/clk/qcom/clk-rcg.h

@@ -167,6 +167,7 @@ struct clk_rcg2_gfx3d {
 
 extern const struct clk_ops clk_rcg2_ops;
 extern const struct clk_ops clk_rcg2_floor_ops;
+extern const struct clk_ops clk_rcg2_mux_closest_ops;
 extern const struct clk_ops clk_edp_pixel_ops;
 extern const struct clk_ops clk_byte_ops;
 extern const struct clk_ops clk_byte2_ops;

drivers/clk/qcom/clk-rcg2.c

@@ -509,6 +509,13 @@ const struct clk_ops clk_rcg2_floor_ops = {
 };
 EXPORT_SYMBOL_GPL(clk_rcg2_floor_ops);
 
+const struct clk_ops clk_rcg2_mux_closest_ops = {
+	.determine_rate = __clk_mux_determine_rate_closest,
+	.get_parent = clk_rcg2_get_parent,
+	.set_parent = clk_rcg2_set_parent,
+};
+EXPORT_SYMBOL_GPL(clk_rcg2_mux_closest_ops);
+
 struct frac_entry {
 	int num;
 	int den;