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-rw-r--r--drivers/clk/clk-vt8500.c73
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;
}