From 765c20456c868989e179b14640ebe65347f2f57a Mon Sep 17 00:00:00 2001 From: Uwe Kleine-König Date: Sat, 21 Feb 2015 11:40:24 +0100 Subject: clk: divider: fix selection of divider when rounding to closest MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit 26bac95aa88c2b1747808c0b885abe7814c0165d upstream. 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-König Acked-by: Sascha Hauer Acked-by: Maxime Coquelin Signed-off-by: Michael Turquette Signed-off-by: Greg Kroah-Hartman --- 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 c0a842b335c5..0c0a865c1266 100644 --- a/drivers/clk/clk-divider.c +++ b/drivers/clk/clk-divider.c @@ -208,6 +208,7 @@ 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); @@ -219,7 +220,10 @@ 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, -- cgit v1.2.3