+Shawn
On 07/31/2015 09:24 AM, Victorien Vedrine wrote:
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.
The issue is reproducible by this way : Set the SAIF frequency to 22579200Hz
(it's the appropriate frequency for 44100hz sample rate for SGTL5000 codec).
With the divider register (HW_CLKCTRL_SAIF0), the closest lower value is
22573242.1875Hz (0xC0A on register). The original clk-frac functions give 0xC09
on the divider register.
Signed-off-by: Victorien Vedrine <[email protected]>
---
drivers/clk/mxs/clk-frac.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/drivers/clk/mxs/clk-frac.c b/drivers/clk/mxs/clk-frac.c
index e6aa6b5..d51cf03 100644
--- a/drivers/clk/mxs/clk-frac.c
+++ b/drivers/clk/mxs/clk-frac.c
@@ -42,11 +42,13 @@ 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 * (u64)div;
We shouldn't need to cast both to 64 bits...
+ return (unsigned long)(tmp_rate >> frac->width);
Isn't the cast implicit by means of the return type of this function?
}
static long clk_frac_round_rate(struct clk_hw *hw, unsigned long rate,
@@ -55,7 +57,7 @@ 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;
@@ -68,7 +70,12 @@ 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 * (u64)div;
+ result = (u64)(tmp_rate >> frac->width);
Cast looks useless here too.
+ if ((result << frac->width) < tmp_rate)
+ return result + 1;
+ else
+ return result;
The else could be dropped and just be return result. Also, have you see
mult_frac()? I suppose we're doing shifts with width because it's a
power-of-2 denominator?
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