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clk: axi-clkgen: Round closest in round_rate() and recalc_rate()

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To minimize the rounding error round to the closest integer when
calculating the result in the recalc_rate() and set_rate() callbacks.

Also in order to improve precision multiply first and then divide.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
This commit is contained in:
Lars-Peter Clausen 2017-09-05 11:32:41 +02:00 committed by Stephen Boyd
parent 063578dc5f
commit 448c3c057a
1 changed files with 7 additions and 3 deletions
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10
drivers/clk/clk-axi-clkgen.c
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@ -302,13 +302,17 @@ static long axi_clkgen_round_rate(struct clk_hw *hw, unsigned long rate,
unsigned long *parent_rate)
{
unsigned int d, m, dout;
unsigned long long tmp;
axi_clkgen_calc_params(*parent_rate, rate, &d, &m, &dout);
if (d == 0 || dout == 0 || m == 0)
return -EINVAL;
return *parent_rate / d * m / dout;
tmp = (unsigned long long)*parent_rate * m;
tmp = DIV_ROUND_CLOSEST_ULL(tmp, dout * d);
return min_t(unsigned long long, tmp, LONG_MAX);
}
static unsigned long axi_clkgen_recalc_rate(struct clk_hw *clk_hw,
@ -344,8 +348,8 @@ static unsigned long axi_clkgen_recalc_rate(struct clk_hw *clk_hw,
if (d == 0 || dout == 0)
return 0;
tmp = (unsigned long long)(parent_rate / d) * m;
do_div(tmp, dout);
tmp = (unsigned long long)parent_rate * m;
tmp = DIV_ROUND_CLOSEST_ULL(tmp, dout * d);
return min_t(unsigned long long, tmp, ULONG_MAX);
}