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authorUwe Kleine-König <u.kleine-koenig@pengutronix.de>2015-02-21 11:40:24 +0100
committerSasha Levin <sasha.levin@oracle.com>2015-04-24 17:14:10 -0400
commit5cd223ea7e47bffef3678605f763a392cbe2623a (patch)
tree5de723e26a6e61d541bd368670fd14feeed45c0c
parentc6aa7146f15eb11c635dbbf48274db04a02241de (diff)
downloadlinux-linaro-stable-5cd223ea7e47bffef3678605f763a392cbe2623a.tar.gz
clk: divider: fix selection of divider when rounding to closest
[ Upstream commit 26bac95aa88c2b1747808c0b885abe7814c0165d ] 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> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
-rw-r--r--drivers/clk/clk-divider.c6
1 files changed, 5 insertions, 1 deletions
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,