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425c08faa8
In some cases, the best config cannot be used because the VCO would be out-of-spec. In these cases, we may need to try a worse combination of r/od in order to find the best representable config. This also adds a few test cases to catch this and other (possible) unlikely errors. Signed-off-by: Sean Anderson <seanga2@gmail.com> Reviewed-by: Simon Glass <sjg@chromium.org>
95 lines
2.5 KiB
C
95 lines
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2020 Sean Anderson <seanga2@gmail.com>
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*/
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#include <common.h>
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/* For DIV_ROUND_DOWN_ULL, defined in linux/kernel.h */
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#include <div64.h>
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#include <dm/test.h>
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#include <kendryte/pll.h>
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#include <test/ut.h>
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static int dm_test_k210_pll_calc_config(u32 rate, u32 rate_in,
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struct k210_pll_config *best)
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{
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u64 f, r, od, max_r, inv_ratio;
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s64 error, best_error;
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best_error = S64_MAX;
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error = best_error;
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max_r = min(16ULL, DIV_ROUND_DOWN_ULL(rate_in, 13300000));
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inv_ratio = DIV_ROUND_CLOSEST_ULL((u64)rate_in << 32, rate);
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/* Brute force it */
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for (r = 1; r <= max_r; r++) {
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for (f = 1; f <= 64; f++) {
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for (od = 1; od <= 16; od++) {
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u64 vco = DIV_ROUND_CLOSEST_ULL(rate_in * f, r);
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if (vco > 1750000000 || vco < 340000000)
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continue;
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error = DIV_ROUND_CLOSEST_ULL(f * inv_ratio,
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r * od);
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/* The lower 16 bits are spurious */
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error = abs((error - BIT(32))) >> 16;
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if (error < best_error) {
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best->r = r;
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best->f = f;
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best->od = od;
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best_error = error;
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}
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}
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}
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}
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if (best_error == S64_MAX)
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return -EINVAL;
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return 0;
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}
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static int dm_test_k210_pll_compare(struct k210_pll_config *ours,
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struct k210_pll_config *theirs)
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{
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return (u32)ours->f * theirs->r * theirs->od !=
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(u32)theirs->f * ours->r * ours->od;
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}
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static int dm_test_k210_pll(struct unit_test_state *uts)
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{
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struct k210_pll_config ours, theirs;
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/* General range checks */
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ut_asserteq(-EINVAL, k210_pll_calc_config(0, 26000000, &theirs));
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ut_asserteq(-EINVAL, k210_pll_calc_config(390000000, 0, &theirs));
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ut_asserteq(-EINVAL, k210_pll_calc_config(2000000000, 26000000,
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&theirs));
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ut_asserteq(-EINVAL, k210_pll_calc_config(390000000, 2000000000,
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&theirs));
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ut_asserteq(-EINVAL, k210_pll_calc_config(1500000000, 20000000,
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&theirs));
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ut_asserteq(-EINVAL, k210_pll_calc_config(1750000000, 13300000,
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&theirs));
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/* Verify we get the same output with brute-force */
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#define compare(rate, rate_in) do { \
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ut_assertok(dm_test_k210_pll_calc_config(rate, rate_in, &ours)); \
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ut_assertok(k210_pll_calc_config(rate, rate_in, &theirs)); \
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ut_assertok(dm_test_k210_pll_compare(&ours, &theirs)); \
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} while (0)
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compare(390000000, 26000000);
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compare(26000000, 390000000);
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compare(400000000, 26000000);
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compare(27000000, 26000000);
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compare(26000000, 27000000);
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compare(13300000 * 64, 13300000);
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compare(21250000, 21250000 * 70);
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compare(21250000, 1750000000);
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compare(1750000000, 1750000000);
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return 0;
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}
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DM_TEST(dm_test_k210_pll, 0);
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