1 files changed, 44 insertions, 55 deletions

diff --git a/drivers/clk/clk-vt8500.c b/drivers/clk/clk-vt8500.c
index b0f76a84f1e9..37368a399ff9 100644
--- a/drivers/clk/clk-vt8500.c
+++ b/drivers/clk/clk-vt8500.c
@@ -383,51 +383,49 @@ 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;
-        u32 best_mul, best_div1, best_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;
-                                        best_mul = mul;
-                                        best_div1 = div1;
-                                        best_div2 = 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);
-        *multiplier = best_mul;
-        *divisor1 = best_div1;
-        *divisor2 = best_div2;
+        pr_warn("%s: rate error is %lu\n", __func__, min_err);
 
         return 0;
 }
@@ -464,7 +462,6 @@ static int wm8750_find_pll_bits(unsigned long rate, unsigned long parent_rate,
 {
         u32 mul;
         int div1, div2;
-        u32 best_mul, best_div1, best_div2;
         unsigned long tclk, rate_err, best_err;
 
         best_err = (unsigned long)-1;
@@ -488,9 +485,9 @@ static int wm8750_find_pll_bits(unsigned long rate, unsigned long parent_rate,
 
                                 if (rate_err < best_err) {
                                         best_err = rate_err;
-                                        best_mul = mul;
-                                        best_div1 = div1;
-                                        best_div2 = div2;
+                                        *multiplier = mul;
+                                        *divisor1 = div1;
+                                        *divisor2 = div2;
                                 }
                         }
 
@@ -503,10 +500,7 @@ static int wm8750_find_pll_bits(unsigned long rate, unsigned long parent_rate,
         pr_warn("%s: requested rate %lu, found rate %lu\n", __func__, rate,
                                                         rate - best_err);
 
-        *filter = wm8750_get_filter(parent_rate, best_div1);
-        *multiplier = best_mul;
-        *divisor1 = best_div1;
-        *divisor2 = best_div2;
+        *filter = wm8750_get_filter(parent_rate, *divisor1);
 
         return 0;
 }
@@ -516,7 +510,6 @@ static int wm8850_find_pll_bits(unsigned long rate, unsigned long parent_rate,
 {
         u32 mul;
         int div1, div2;
-        u32 best_mul, best_div1, best_div2;
         unsigned long tclk, rate_err, best_err;
 
         best_err = (unsigned long)-1;
@@ -540,9 +533,9 @@ static int wm8850_find_pll_bits(unsigned long rate, unsigned long parent_rate,
 
                                 if (rate_err < best_err) {
                                         best_err = rate_err;
-                                        best_mul = mul;
-                                        best_div1 = div1;
-                                        best_div2 = div2;
+                                        *multiplier = mul;
+                                        *divisor1 = div1;
+                                        *divisor2 = div2;
                                 }
                         }
 
@@ -555,10 +548,6 @@ static int wm8850_find_pll_bits(unsigned long rate, unsigned long parent_rate,
         pr_warn("%s: requested rate %lu, found rate %lu\n", __func__, rate,
                                                         rate - best_err);
 
-        *multiplier = best_mul;
-        *divisor1 = best_div1;
-        *divisor2 = best_div2;
-
         return 0;
 }