test/dm/k210_pll.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2020 Sean Anderson <seanga2@gmail.com>
   4  */
   5
   6 #include <common.h>
   7 /* For DIV_ROUND_DOWN_ULL, defined in linux/kernel.h */
   8 #include <div64.h>
   9 #include <dm/test.h>
  10 #include <kendryte/pll.h>
  11 #include <test/ut.h>
  12
  13 static int dm_test_k210_pll_calc_config(u32 rate, u32 rate_in,
  14                                         struct k210_pll_config *best)
  15 {
  16         u64 f, r, od, max_r, inv_ratio;
  17         s64 error, best_error;
  18
  19         best_error = S64_MAX;
  20         error = best_error;
  21         max_r = min(16ULL, DIV_ROUND_DOWN_ULL(rate_in, 13300000));
  22         inv_ratio = DIV_ROUND_CLOSEST_ULL((u64)rate_in << 32, rate);
  23
  24         /* Brute force it */
  25         for (r = 1; r <= max_r; r++) {
  26                 for (f = 1; f <= 64; f++) {
  27                         for (od = 1; od <= 16; od++) {
  28                                 u64 vco = DIV_ROUND_CLOSEST_ULL(rate_in * f, r);
  29
  30                                 if (vco > 1750000000 || vco < 340000000)
  31                                         continue;
  32
  33                                 error = DIV_ROUND_CLOSEST_ULL(f * inv_ratio,
  34                                                               r * od);
  35                                 /* The lower 16 bits are spurious */
  36                                 error = abs((error - BIT(32))) >> 16;
  37                                 if (error < best_error) {
  38                                         best->r = r;
  39                                         best->f = f;
  40                                         best->od = od;
  41                                         best_error = error;
  42                                 }
  43                         }
  44                 }
  45         }
  46
  47         if (best_error == S64_MAX)
  48                 return -EINVAL;
  49         return 0;
  50 }
  51
  52 static int dm_test_k210_pll_compare(struct k210_pll_config *ours,
  53                                     struct k210_pll_config *theirs)
  54 {
  55         return (u32)ours->f * theirs->r * theirs->od !=
  56                (u32)theirs->f * ours->r * ours->od;
  57 }
  58
  59 static int dm_test_k210_pll(struct unit_test_state *uts)
  60 {
  61         struct k210_pll_config ours, theirs;
  62
  63         /* General range checks */
  64         ut_asserteq(-EINVAL, k210_pll_calc_config(0, 26000000, &theirs));
  65         ut_asserteq(-EINVAL, k210_pll_calc_config(390000000, 0, &theirs));
  66         ut_asserteq(-EINVAL, k210_pll_calc_config(2000000000, 26000000,
  67                                                   &theirs));
  68         ut_asserteq(-EINVAL, k210_pll_calc_config(390000000, 2000000000,
  69                                                   &theirs));
  70         ut_asserteq(-EINVAL, k210_pll_calc_config(1500000000, 20000000,
  71                                                   &theirs));
  72         ut_asserteq(-EINVAL, k210_pll_calc_config(1750000000, 13300000,
  73                                                   &theirs));
  74
  75         /* Verify we get the same output with brute-force */
  76 #define compare(rate, rate_in) do { \
  77         ut_assertok(dm_test_k210_pll_calc_config(rate, rate_in, &ours)); \
  78         ut_assertok(k210_pll_calc_config(rate, rate_in, &theirs)); \
  79         ut_assertok(dm_test_k210_pll_compare(&ours, &theirs)); \
  80 } while (0)
  81
  82         compare(390000000, 26000000);
  83         compare(26000000, 390000000);
  84         compare(400000000, 26000000);
  85         compare(27000000, 26000000);
  86         compare(26000000, 27000000);
  87
  88         return 0;
  89 }
  90 DM_TEST(dm_test_k210_pll, 0);