From 448c3c057a1dbb6ecf6e507a3f1a58f5eab21560 Mon Sep 17 00:00:00 2001 From: Lars-Peter Clausen Date: Tue, 5 Sep 2017 11:32:41 +0200 Subject: [PATCH] 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 Signed-off-by: Stephen Boyd --- drivers/clk/clk-axi-clkgen.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/clk/clk-axi-clkgen.c b/drivers/clk/clk-axi-clkgen.c index 95a6e9834392..48d11f2598e8 100644 --- a/drivers/clk/clk-axi-clkgen.c +++ b/drivers/clk/clk-axi-clkgen.c @@ -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); }