[PATCH 2/3] clk: divider: Fix best div calculation for power-of-two and table dividers

[Marcin Niestroj <m.niestroj@xxxxxxxxxxxxxxxx>]

commit dd23c2cd38da2c64af381b19795d2c4f115e8ecb Linux upstream.

  clk: divider: Fix best div calculation for power-of-two and table dividers

  The divider returned by clk_divider_bestdiv() is likely to be invalid in case
  of power-of-two and table dividers when CLK_SET_RATE_PARENT flag isn't set.

  Fixes boot on STiH416 platform.

  Signed-off-by: Maxime Coquelin <maxime.coquelin@xxxxxx>
  Signed-off-by: Mike Turquette <mturquette@xxxxxxxxxx>
  [mturquette@xxxxxxxxxx: trivial merge conflict & updated changelog]

Signed-off-by: Marcin Niestroj <m.niestroj@xxxxxxxxxxxxxxxx>
---
 drivers/clk/clk-divider.c | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index 84a5322cf..d705729af 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -141,6 +141,37 @@ static bool _is_valid_div(struct clk_divider *divider, unsigned int div)
 	return true;
 }
 
+static int _round_up_table(const struct clk_div_table *table, int div)
+{
+	const struct clk_div_table *clkt;
+	int up = _get_table_maxdiv(table);
+
+	for (clkt = table; clkt->div; clkt++) {
+		if (clkt->div == div)
+			return clkt->div;
+		else if (clkt->div < div)
+			continue;
+
+		if ((clkt->div - div) < (up - div))
+			up = clkt->div;
+	}
+
+	return up;
+}
+
+static int _div_round_up(struct clk_divider *divider,
+		unsigned long parent_rate, unsigned long rate)
+{
+	int div = DIV_ROUND_UP(parent_rate, rate);
+
+	if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
+		div = __roundup_pow_of_two(div);
+	if (divider->table)
+		div = _round_up_table(divider->table, div);
+
+	return div;
+}
+
 static int clk_divider_bestdiv(struct clk *clk, unsigned long rate,
 		unsigned long *best_parent_rate)
 {
@@ -156,7 +187,7 @@ static int clk_divider_bestdiv(struct clk *clk, unsigned long rate,
 
 	if (!(clk->flags & CLK_SET_RATE_PARENT)) {
 		parent_rate = *best_parent_rate;
-		bestdiv = DIV_ROUND_UP(parent_rate, rate);
+		bestdiv = _div_round_up(divider, parent_rate, rate);
 		bestdiv = bestdiv == 0 ? 1 : bestdiv;
 		bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
 		return bestdiv;
@@ -230,6 +261,9 @@ static int clk_divider_set_rate(struct clk *clk, unsigned long rate,
 		div = DIV_ROUND_UP(parent_rate, rate);
 	}
 
+	if (!_is_valid_div(divider->table, div, divider->flags))
+		return -EINVAL;
+
 	value = _get_val(divider, div);
 
 	if (value > div_mask(divider))
-- 
2.21.0


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