From d87574332cd669c8949b75e87e499a7478dffead Mon Sep 17 00:00:00 2001 From: Victorien Vedrine Date: Mon, 31 Aug 2015 10:45:07 +0200 Subject: [PATCH] clk:mxs: Fix bug on frequency divider On drivers/clk/mxs/clk-frac.c, the function clk_frac_round_rate returned a bad result. The division before multiplication computes a wrong value ; the calculation is inverted to fix the problem. The second issue is that the exact rate have decimals and they are truncate. The consequence is that the function clk_frac_set_rate (which use the result of clk_frac_round_rate) computes a wrong value for the register (the rate generated can be closer to the desired rate). The correction is : if there is decimal to the result, it is rounded to the next larger integer. On drivers/clk/mxs/clk-frac.c, the function clk_frac_recalc_rate returned a bad result. The multiplication is made before the division to compute a correct value. Signed-off-by: Victorien Vedrine Acked-by: Shawn Guo Signed-off-by: Stephen Boyd --- drivers/clk/mxs/clk-frac.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/clk/mxs/clk-frac.c b/drivers/clk/mxs/clk-frac.c index 73f0240569ac..f8dd10f6df3d 100644 --- a/drivers/clk/mxs/clk-frac.c +++ b/drivers/clk/mxs/clk-frac.c @@ -41,11 +41,13 @@ static unsigned long clk_frac_recalc_rate(struct clk_hw *hw, { struct clk_frac *frac = to_clk_frac(hw); u32 div; + u64 tmp_rate; div = readl_relaxed(frac->reg) >> frac->shift; div &= (1 << frac->width) - 1; - return (parent_rate >> frac->width) * div; + tmp_rate = (u64)parent_rate * div; + return tmp_rate >> frac->width; } static long clk_frac_round_rate(struct clk_hw *hw, unsigned long rate, @@ -54,7 +56,7 @@ static long clk_frac_round_rate(struct clk_hw *hw, unsigned long rate, struct clk_frac *frac = to_clk_frac(hw); unsigned long parent_rate = *prate; u32 div; - u64 tmp; + u64 tmp, tmp_rate, result; if (rate > parent_rate) return -EINVAL; @@ -67,7 +69,11 @@ static long clk_frac_round_rate(struct clk_hw *hw, unsigned long rate, if (!div) return -EINVAL; - return (parent_rate >> frac->width) * div; + tmp_rate = (u64)parent_rate * div; + result = tmp_rate >> frac->width; + if ((result << frac->width) < tmp_rate) + result += 1; + return result; } static int clk_frac_set_rate(struct clk_hw *hw, unsigned long rate, -- 2.34.1