From: Uwe Kleine-König Date: Sat, 21 Feb 2015 10:40:24 +0000 (+0100) Subject: clk: divider: fix selection of divider when rounding to closest X-Git-Tag: v4.0-rc4~2^2~6 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=26bac95aa88c2b1747808c0b885abe7814c0165d;p=linux.git clk: divider: fix selection of divider when rounding to closest 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 --- diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c index a1a029092c8d..78b2e656ff6a 100644 --- a/drivers/clk/clk-divider.c +++ b/drivers/clk/clk-divider.c @@ -220,6 +220,7 @@ static int _div_round_closest(const struct clk_div_table *table, unsigned long flags) { int up, down, div; + unsigned long up_rate, down_rate; up = down = div = DIV_ROUND_CLOSEST(parent_rate, rate); @@ -231,7 +232,10 @@ static int _div_round_closest(const struct clk_div_table *table, down = _round_down_table(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(const struct clk_div_table *table,