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 /* For DIV_ROUND_DOWN_ULL, defined in linux/kernel.h */
   7 #include <div64.h>
   8 #include <dm/test.h>
   9 #include <k210/pll.h>
  10 #include <test/ut.h>
  11
  12 static int dm_test_k210_pll_calc_config(u32 rate, u32 rate_in,
  13                                         struct k210_pll_config *best)
  14 {
  15         u64 f, r, od, max_r, inv_ratio;
  16         s64 error, best_error;
  17
  18         best_error = S64_MAX;
  19         error = best_error;
  20         max_r = min(16ULL, DIV_ROUND_DOWN_ULL(rate_in, 13300000));
  21         inv_ratio = DIV_ROUND_CLOSEST_ULL((u64)rate_in << 32, rate);
  22
  23         /* Brute force it */
  24         for (r = 1; r <= max_r; r++) {
  25                 for (f = 1; f <= 64; f++) {
  26                         for (od = 1; od <= 16; od++) {
  27                                 u64 vco = DIV_ROUND_CLOSEST_ULL(rate_in * f, r);
  28
  29                                 if (vco > 1750000000 || vco < 340000000)
  30                                         continue;
  31
  32                                 error = DIV_ROUND_CLOSEST_ULL(f * inv_ratio,
  33                                                               r * od);
  34                                 /* The lower 16 bits are spurious */
  35                                 error = abs64((error - BIT_ULL(32))) >> 16;
  36                                 if (error < best_error) {
  37                                         best->r = r;
  38                                         best->f = f;
  39                                         best->od = od;
  40                                         best_error = error;
  41                                 }
  42                         }
  43                 }
  44         }
  45
  46         if (best_error == S64_MAX)
  47                 return -EINVAL;
  48         return 0;
  49 }
  50
  51 static int dm_test_k210_pll_compare(struct k210_pll_config *ours,
  52                                     struct k210_pll_config *theirs)
  53 {
  54         return (u32)ours->f * theirs->r * theirs->od !=
  55                (u32)theirs->f * ours->r * ours->od;
  56 }
  57
  58 static int dm_test_k210_pll(struct unit_test_state *uts)
  59 {
  60         struct k210_pll_config ours, theirs;
  61
  62         /* General range checks */
  63         ut_asserteq(-EINVAL, k210_pll_calc_config(0, 26000000, &theirs));
  64         ut_asserteq(-EINVAL, k210_pll_calc_config(390000000, 0, &theirs));
  65         ut_asserteq(-EINVAL, k210_pll_calc_config(2000000000, 26000000,
  66                                                   &theirs));
  67         ut_asserteq(-EINVAL, k210_pll_calc_config(390000000, 2000000000,
  68                                                   &theirs));
  69         ut_asserteq(-EINVAL, k210_pll_calc_config(1500000000, 20000000,
  70                                                   &theirs));
  71         ut_asserteq(-EINVAL, k210_pll_calc_config(1750000000, 13300000,
  72                                                   &theirs));
  73
  74         /* Verify we get the same output with brute-force */
  75 #define compare(rate, rate_in) do { \
  76         ut_assertok(dm_test_k210_pll_calc_config(rate, rate_in, &ours)); \
  77         ut_assertok(k210_pll_calc_config(rate, rate_in, &theirs)); \
  78         ut_assertok(dm_test_k210_pll_compare(&ours, &theirs)); \
  79 } while (0)
  80
  81         compare(390000000, 26000000);
  82         compare(26000000, 390000000);
  83         compare(400000000, 26000000);
  84         compare(27000000, 26000000);
  85         compare(26000000, 27000000);
  86         compare(13300000 * 64, 13300000);
  87         compare(21250000, 21250000 * 70);
  88         compare(21250000, 1750000000);
  89         compare(1750000000, 1750000000);
  90
  91         return 0;
  92 }
  93 DM_TEST(dm_test_k210_pll, 0);