Commit 93155142 authored by Uwe Kleine-König's avatar Uwe Kleine-König Committed by Michael Turquette

clk: divider: fix calculation of initial best divider when rounding to closest

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: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: default avatarSascha Hauer <s.hauer@pengutronix.de>
Acked-by: default avatarMaxime Coquelin <maxime.coquelin@st.com>
Signed-off-by: default avatarMichael Turquette <mturquette@linaro.org>
parent 26bac95a
...@@ -219,17 +219,18 @@ static int _div_round_closest(const struct clk_div_table *table, ...@@ -219,17 +219,18 @@ static int _div_round_closest(const struct clk_div_table *table,
unsigned long parent_rate, unsigned long rate, unsigned long parent_rate, unsigned long rate,
unsigned long flags) unsigned long flags)
{ {
int up, down, div; int up, down;
unsigned long up_rate, down_rate; 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) { if (flags & CLK_DIVIDER_POWER_OF_TWO) {
up = __roundup_pow_of_two(div); up = __roundup_pow_of_two(up);
down = __rounddown_pow_of_two(div); down = __rounddown_pow_of_two(down);
} else if (table) { } else if (table) {
up = _round_up_table(table, div); up = _round_up_table(table, up);
down = _round_down_table(table, div); down = _round_down_table(table, down);
} }
up_rate = DIV_ROUND_UP(parent_rate, up); up_rate = DIV_ROUND_UP(parent_rate, up);
......
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