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 <victorien.vedrine@ophrys.net>
Acked-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

diff --git a/drivers/clk/mxs/clk-frac.c b/drivers/clk/mxs/clk-frac.c
index 73f0240..f8dd10f 100644 (file)
--- 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,