clk: divider: Make divider_round_rate take the parent clock

So far, divider_round_rate only considers the parent clock returned by
clk_hw_get_parent.

This works fine on clocks that have a single parents, this doesn't work on
muxes, since we will only consider the first parent, while other parents
may totally be able to provide a better combination.

Clocks in that case cannot use divider_round_rate, so would have to come up
with a very similar logic to work around it. Instead of having to do
something like this, and duplicate that logic everywhere, create a
divider_round_rate parent to allow caller to give an additional parameter
for the parent clock to consider.
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>

drivers/clk/clk-divider.c

@@ -275,7 +275,8 @@ static int _next_div(const struct clk_div_table *table, int div,
 	return div;
 }
 
-static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
+static int clk_divider_bestdiv(struct clk_hw *hw, struct clk_hw *parent,
+			       unsigned long rate,
 			       unsigned long *best_parent_rate,
 			       const struct clk_div_table *table, u8 width,
 			       unsigned long flags)
@@ -314,8 +315,7 @@ static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
 			*best_parent_rate = parent_rate_saved;
 			return i;
 		}
-		parent_rate = clk_hw_round_rate(clk_hw_get_parent(hw),
-					       rate * i);
+		parent_rate = clk_hw_round_rate(parent, rate * i);
 		now = DIV_ROUND_UP_ULL((u64)parent_rate, i);
 		if (_is_best_div(rate, now, best, flags)) {
 			bestdiv = i;
@@ -326,23 +326,24 @@ static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
 
 	if (!bestdiv) {
 		bestdiv = _get_maxdiv(table, width, flags);
-		*best_parent_rate = clk_hw_round_rate(clk_hw_get_parent(hw), 1);
+		*best_parent_rate = clk_hw_round_rate(parent, 1);
 	}
 
 	return bestdiv;
 }
 
-long divider_round_rate(struct clk_hw *hw, unsigned long rate,
-			unsigned long *prate, const struct clk_div_table *table,
+long divider_round_rate_parent(struct clk_hw *hw, struct clk_hw *parent,
+			       unsigned long rate, unsigned long *prate,
+			       const struct clk_div_table *table,
 			       u8 width, unsigned long flags)
 {
 	int div;
 
-	div = clk_divider_bestdiv(hw, rate, prate, table, width, flags);
+	div = clk_divider_bestdiv(hw, parent, rate, prate, table, width, flags);
 
 	return DIV_ROUND_UP_ULL((u64)*prate, div);
 }
-EXPORT_SYMBOL_GPL(divider_round_rate);
+EXPORT_SYMBOL_GPL(divider_round_rate_parent);
 
 static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
 				unsigned long *prate)

include/linux/clk-provider.h

@@ -412,8 +412,9 @@ extern const struct clk_ops clk_divider_ro_ops;
 unsigned long divider_recalc_rate(struct clk_hw *hw, unsigned long parent_rate,
 		unsigned int val, const struct clk_div_table *table,
 		unsigned long flags);
-long divider_round_rate(struct clk_hw *hw, unsigned long rate,
-		unsigned long *prate, const struct clk_div_table *table,
+long divider_round_rate_parent(struct clk_hw *hw, struct clk_hw *parent,
+			       unsigned long rate, unsigned long *prate,
+			       const struct clk_div_table *table,
 			       u8 width, unsigned long flags);
 int divider_get_val(unsigned long rate, unsigned long parent_rate,
 		const struct clk_div_table *table, u8 width,
@@ -757,6 +758,15 @@ static inline void __clk_hw_set_clk(struct clk_hw *dst, struct clk_hw *src)
 	dst->core = src->core;
 }
 
+static inline long divider_round_rate(struct clk_hw *hw, unsigned long rate,
+				      unsigned long *prate,
+				      const struct clk_div_table *table,
+				      u8 width, unsigned long flags)
+{
+	return divider_round_rate_parent(hw, clk_hw_get_parent(hw),
+					 rate, prate, table, width, flags);
+}
+
 /*
  * FIXME clock api without lock protection
  */