clk: axi-clkgen: Round closest in round_rate() and recalc_rate()
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>
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@ -302,13 +302,17 @@ static long axi_clkgen_round_rate(struct clk_hw *hw, unsigned long rate,
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unsigned long *parent_rate)
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{
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unsigned int d, m, dout;
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unsigned long long tmp;
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axi_clkgen_calc_params(*parent_rate, rate, &d, &m, &dout);
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if (d == 0 || dout == 0 || m == 0)
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return -EINVAL;
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return *parent_rate / d * m / dout;
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tmp = (unsigned long long)*parent_rate * m;
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tmp = DIV_ROUND_CLOSEST_ULL(tmp, dout * d);
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return min_t(unsigned long long, tmp, LONG_MAX);
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}
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static unsigned long axi_clkgen_recalc_rate(struct clk_hw *clk_hw,
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@ -344,8 +348,8 @@ static unsigned long axi_clkgen_recalc_rate(struct clk_hw *clk_hw,
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if (d == 0 || dout == 0)
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return 0;
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tmp = (unsigned long long)(parent_rate / d) * m;
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do_div(tmp, dout);
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tmp = (unsigned long long)parent_rate * m;
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tmp = DIV_ROUND_CLOSEST_ULL(tmp, dout * d);
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return min_t(unsigned long long, tmp, ULONG_MAX);
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}
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