[RFC PATCH] clk: composite: support determine_rate using rate_ops->round_rate + mux_ops->set_parent

[Boris BREZILLON]

In case the rate_hw does not implement determine_rate, but only round_rate
we fallback to best_parent selection if mux_hw is present and support
reparenting.

Signed-off-by: Boris BREZILLON <b.brezillon at overkiz.com>
---
 drivers/clk/clk-composite.c |   49 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 48 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk-composite.c b/drivers/clk/clk-composite.c
index 753d0b7..d3cf49a 100644
--- a/drivers/clk/clk-composite.c
+++ b/drivers/clk/clk-composite.c
@@ -64,11 +64,57 @@ static long clk_composite_determine_rate(struct clk_hw *hw, unsigned long rate,
 	const struct clk_ops *mux_ops = composite->mux_ops;
 	struct clk_hw *rate_hw = composite->rate_hw;
 	struct clk_hw *mux_hw = composite->mux_hw;
+	struct clk *parent;
+	unsigned long parent_rate;
+	long tmp_rate;
+	unsigned long rate_diff;
+	unsigned long best_rate_diff = ULONG_MAX;
+	int i;
 
 	if (rate_hw && rate_ops && rate_ops->determine_rate) {
 		rate_hw->clk = hw->clk;
 		return rate_ops->determine_rate(rate_hw, rate, best_parent_rate,
 						best_parent_p);
+	} else if (rate_hw && rate_ops && rate_ops->round_rate &&
+		   mux_hw && mux_ops && mux_ops->set_parent) {
+		*best_parent_p = NULL;
+
+		if (__clk_get_flags(hw->clk) & CLK_SET_RATE_NO_REPARENT) {
+			*best_parent_p = clk_get_parent(mux_hw->clk);
+			*best_parent_rate = __clk_get_rate(*best_parent_p);
+
+			return rate_ops->round_rate(rate_hw, rate,
+						    best_parent_rate);
+		}
+
+		for (i = 0; i < __clk_get_num_parents(mux_hw->clk); i++) {
+			parent = clk_get_parent_by_index(mux_hw->clk, i);
+			if (!parent)
+				continue;
+
+			parent_rate = __clk_get_rate(parent);
+
+			tmp_rate = rate_ops->round_rate(rate_hw, rate,
+							&parent_rate);
+			if (tmp_rate < 0)
+				continue;
+
+			if (tmp_rate < rate)
+				rate_diff = rate - tmp_rate;
+			else
+				rate_diff = tmp_rate - rate;
+
+			if (!rate_diff || !*best_parent_p || best_rate_diff > rate_diff) {
+				*best_parent_p = parent;
+				*best_parent_rate = parent_rate;
+				best_rate_diff = rate_diff;
+			}
+
+			if (!rate_diff)
+				return rate;
+		}
+
+		return best_rate_diff;
 	} else if (mux_hw && mux_ops && mux_ops->determine_rate) {
 		mux_hw->clk = hw->clk;
 		return mux_ops->determine_rate(rate_hw, rate, best_parent_rate,
@@ -196,7 +242,8 @@ struct clk *clk_register_composite(struct device *dev, const char *name,
 		composite->rate_hw = rate_hw;
 		composite->rate_ops = rate_ops;
 		clk_composite_ops->recalc_rate = clk_composite_recalc_rate;
-		if (rate_ops->determine_rate)
+		if (rate_ops->determine_rate ||
+		    (rate_ops->round_rate && clk_composite_ops->set_parent))
 			clk_composite_ops->determine_rate = clk_composite_determine_rate;
 	}
 
-- 
1.7.9.5