[PATCH] clk: ingenic: Fix divider calculation with div tables

[PATCH] clk: ingenic: Fix divider calculation with div tables

[Paul Cercueil]

The previous code assumed that a higher hardware value always resulted
in a bigger divider, which is correct for the regular clocks, but is
an invalid assumption when a divider table is provided for the clock.

Perfect example of this is the PLL0_HALF clock, which applies a /2
divider with the hardware value 0, and a /1 divider otherwise.

Fixes: a9fa2893fcc6 ("clk: ingenic: Add support for divider tables")
Cc: <stable@vger.kernel.org> # 5.2
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
---
 drivers/clk/ingenic/cgu.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/clk/ingenic/cgu.c b/drivers/clk/ingenic/cgu.c
index dac6edc670cc..c8e9cb6c8e39 100644
--- a/drivers/clk/ingenic/cgu.c
+++ b/drivers/clk/ingenic/cgu.c
@@ -392,15 +392,21 @@ static unsigned int
 ingenic_clk_calc_hw_div(const struct ingenic_cgu_clk_info *clk_info,
 			unsigned int div)
 {
-	unsigned int i;
+	unsigned int i, best_i = 0, best = (unsigned int)-1;
 
 	for (i = 0; i < (1 << clk_info->div.bits)
 				&& clk_info->div.div_table[i]; i++) {
-		if (clk_info->div.div_table[i] >= div)
-			return i;
+		if (clk_info->div.div_table[i] >= div &&
+		    clk_info->div.div_table[i] < best) {
+			best = clk_info->div.div_table[i];
+			best_i = i;
+
+			if (div == best)
+				break;
+		}
 	}
 
-	return i - 1;
+	return best_i;
 }
 
 static unsigned
-- 
2.29.2

Re: [PATCH] clk: ingenic: Fix divider calculation with div tables

[Stephen Boyd]

Quoting Paul Cercueil (2020-12-12 05:57:33)
> The previous code assumed that a higher hardware value always resulted
> in a bigger divider, which is correct for the regular clocks, but is
> an invalid assumption when a divider table is provided for the clock.
> 
> Perfect example of this is the PLL0_HALF clock, which applies a /2
> divider with the hardware value 0, and a /1 divider otherwise.
> 
> Fixes: a9fa2893fcc6 ("clk: ingenic: Add support for divider tables")
> Cc: <stable@vger.kernel.org> # 5.2
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> ---

Applied to clk-next