diff options
| -rw-r--r-- | drivers/clk/clk-vt8500.c | 73 |
1 files changed, 38 insertions, 35 deletions
diff --git a/drivers/clk/clk-vt8500.c b/drivers/clk/clk-vt8500.c index d5a3453970d0..37368a399ff9 100644 --- a/drivers/clk/clk-vt8500.c +++ b/drivers/clk/clk-vt8500.c @@ -383,47 +383,50 @@ static int vt8500_find_pll_bits(unsigned long rate, unsigned long parent_rate, return 0; } -static int wm8650_find_pll_bits(unsigned long rate, unsigned long parent_rate, - u32 *multiplier, u32 *divisor1, u32 *divisor2) +/* + * M * parent [O1] => / P [O2] => / D [O3] + * Where O1 is 900MHz...3GHz; + * O2 is 600MHz >= (M * parent) / P >= 300MHz; + * M is 36...120 [25MHz parent]; D is 1 or 2 or 4 or 8. + * Possible ranges (O3): + * D = 8: 37,5MHz...75MHz + * D = 4: 75MHz...150MHz + * D = 2: 150MHz...300MHz + * D = 1: 300MHz...600MHz + */ +static int wm8650_find_pll_bits(unsigned long rate, + unsigned long parent_rate, u32 *multiplier, u32 *divisor1, + u32 *divisor2) { - u32 mul, div1; - int div2; - unsigned long tclk, rate_err, best_err; - - best_err = (unsigned long)-1; + unsigned long O1, min_err, rate_err; - /* Find the closest match (lower or equal to requested) */ - for (div1 = 5; div1 >= 3; div1--) - for (div2 = 3; div2 >= 0; div2--) - for (mul = 3; mul <= 1023; mul++) { - tclk = parent_rate * mul / (div1 * (1 << div2)); - if (tclk > rate) - continue; - /* error will always be +ve */ - rate_err = rate - tclk; - if (rate_err == 0) { - *multiplier = mul; - *divisor1 = div1; - *divisor2 = div2; - return 0; - } + if (!parent_rate || (rate < 37500000) || (rate > 600000000)) + return -EINVAL; - if (rate_err < best_err) { - best_err = rate_err; - *multiplier = mul; - *divisor1 = div1; - *divisor2 = div2; - } - } + *divisor2 = rate <= 75000000 ? 3 : rate <= 150000000 ? 2 : + rate <= 300000000 ? 1 : 0; + /* + * Divisor P cannot be calculated. Test all divisors and find where M + * will be as close as possible to the requested rate. + */ + min_err = ULONG_MAX; + for (*divisor1 = 5; *divisor1 >= 3; (*divisor1)--) { + O1 = rate * *divisor1 * (1 << (*divisor2)); + rate_err = O1 % parent_rate; + if (rate_err < min_err) { + *multiplier = O1 / parent_rate; + if (rate_err == 0) + return 0; + + min_err = rate_err; + } + } - if (best_err == (unsigned long)-1) { - pr_warn("%s: impossible rate %lu\n", __func__, rate); + if ((*multiplier < 3) || (*multiplier > 1023)) return -EINVAL; - } - /* if we got here, it wasn't an exact match */ - pr_warn("%s: requested rate %lu, found rate %lu\n", __func__, rate, - rate - best_err); + pr_warn("%s: rate error is %lu\n", __func__, min_err); + return 0; } |