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| author | Victorien Vedrine <victorien.vedrine@ophrys.net> | 2015-08-31 10:45:07 +0200 |
|---|---|---|
| committer | Stephen Boyd <sboyd@codeaurora.org> | 2015-10-01 15:24:34 -0700 |
| commit | d87574332cd669c8949b75e87e499a7478dffead (patch) | |
| tree | 90dce79afe43232a64cf6f6941d00817565cfb85 /drivers/clk/mxs | |
| parent | a1c22a4be7983f64324e960f7ba373784c0c8289 (diff) | |
| download | lwn-d87574332cd669c8949b75e87e499a7478dffead.tar.gz lwn-d87574332cd669c8949b75e87e499a7478dffead.zip | |
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>
Diffstat (limited to 'drivers/clk/mxs')
| -rw-r--r-- | drivers/clk/mxs/clk-frac.c | 12 |
1 files 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, |