[PATCH 2/3] clk: divider: fix selection of divider when rounding to closest
From: Uwe Kleine-König <hidden>
Date: 2015-02-21 10:40:34
Also in:
lkml
Subsystem:
common clk framework, the rest · Maintainers:
Michael Turquette, Stephen Boyd, Linus Torvalds
It's an invalid approach to assume that among two divider values the one nearer the exact divider is the better one. Assume a parent rate of 1000 Hz, a divider with CLK_DIVIDER_POWER_OF_TWO and a target rate of 89 Hz. The exact divider is ~ 11.236 so 8 and 16 are the candidates to choose from yielding rates 125 Hz and 62.5 Hz respectivly. While 8 is nearer to 11.236 than 16 is, the latter is still the better divider as 62.5 is nearer to 89 than 125 is. Fixes: 774b514390b1 (clk: divider: Add round to closest divider) Signed-off-by: Uwe Kleine-K?nig <redacted> --- drivers/clk/clk-divider.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index fbd9e8270791..66a6211b8834 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c@@ -202,6 +202,7 @@ static int _div_round_closest(struct clk_divider *divider, unsigned long parent_rate, unsigned long rate) { int up, down, div; + unsigned long up_rate, down_rate; up = down = div = DIV_ROUND_CLOSEST(parent_rate, rate);
@@ -213,7 +214,10 @@ static int _div_round_closest(struct clk_divider *divider, down = _round_down_table(divider->table, div); } - return (up - div) <= (div - down) ? up : down; + up_rate = DIV_ROUND_UP(parent_rate, up); + down_rate = DIV_ROUND_UP(parent_rate, down); + + return (rate - up_rate) <= (down_rate - rate) ? up : down; } static int _div_round(struct clk_divider *divider, unsigned long parent_rate,
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2.1.4