From 9315514252a95bca37be3ef8a93f835ed91c2855 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Uwe=20Kleine-K=C3=B6nig?= Date: Sat, 21 Feb 2015 11:40:25 +0100 Subject: [PATCH] clk: divider: fix calculation of initial best divider when rounding to closest MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Similar to the reasoning for the previous commit DIV_ROUND_CLOSEST(parent_rate, rate) might not be the best integer divisor to get a good approximation for rate from parent_rate (given the metric for CLK_DIVIDER_ROUND_CLOSEST). For example assume a parent rate of 1000 Hz and a target rate of 700. Using DIV_ROUND_CLOSEST the suggested divisor gets calculated to 1 resulting in a target rate of 1000 with a delta of 300 to the desired rate. With choosing 2 as divisor however the resulting rate is 500 which is nearer to 700. Signed-off-by: Uwe Kleine-König Acked-by: Sascha Hauer Acked-by: Maxime Coquelin Signed-off-by: Michael Turquette --- drivers/clk/clk-divider.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c index 78b2e656ff6a..25006a8bb8e6 100644 --- a/drivers/clk/clk-divider.c +++ b/drivers/clk/clk-divider.c @@ -219,17 +219,18 @@ static int _div_round_closest(const struct clk_div_table *table, unsigned long parent_rate, unsigned long rate, unsigned long flags) { - int up, down, div; + int up, down; unsigned long up_rate, down_rate; - up = down = div = DIV_ROUND_CLOSEST(parent_rate, rate); + up = DIV_ROUND_UP(parent_rate, rate); + down = parent_rate / rate; if (flags & CLK_DIVIDER_POWER_OF_TWO) { - up = __roundup_pow_of_two(div); - down = __rounddown_pow_of_two(div); + up = __roundup_pow_of_two(up); + down = __rounddown_pow_of_two(down); } else if (table) { - up = _round_up_table(table, div); - down = _round_down_table(table, div); + up = _round_up_table(table, up); + down = _round_down_table(table, down); } up_rate = DIV_ROUND_UP(parent_rate, up); -- 2.39.2