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| author | Uwe Kleine-König <u.kleine-koenig@pengutronix.de> | 2015-02-21 13:40:24 +0300 |
|---|---|---|
| committer | Michael Turquette <mturquette@linaro.org> | 2015-03-10 00:19:54 +0300 |
| commit | 26bac95aa88c2b1747808c0b885abe7814c0165d (patch) | |
| tree | e5b94aca44f42c17cdef858f1c8782a625769c5e /drivers/clk/clk-divider.c | |
| parent | da321133b53caf7889ed3ca1dabe4cc368db2604 (diff) | |
| download | linux-26bac95aa88c2b1747808c0b885abe7814c0165d.tar.xz | |
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 <u.kleine-koenig@pengutronix.de>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Maxime Coquelin <maxime.coquelin@st.com>
Signed-off-by: Michael Turquette <mturquette@linaro.org>
Diffstat (limited to 'drivers/clk/clk-divider.c')
| -rw-r--r-- | drivers/clk/clk-divider.c | 6 |
1 files changed, 5 insertions, 1 deletions
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, |