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fix(hal): prevent overflow in fractional clock division

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Co-authored-by: Cursor <cursoragent@cursor.com>
This commit is contained in:
Chen Chen
2026-07-30 17:04:17 +08:00
parent 4065b2ed8f
commit 4f9e257c77
2 changed files with 15 additions and 6 deletions
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11
components/hal/hal_utils.c
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@@ -1,5 +1,5 @@
/*
* SPDX-FileCopyrightText: 2023-2024 Espressif Systems (Shanghai) CO LTD
* SPDX-FileCopyrightText: 2023-2026 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
@@ -16,7 +16,7 @@
#endif
__attribute__((always_inline))
static inline uint32_t _sub_abs(uint32_t a, uint32_t b)
static inline uint64_t _sub_abs(uint64_t a, uint64_t b)
{
return a > b ? a - b : b - a;
}
@@ -78,9 +78,10 @@ uint32_t hal_utils_calc_clk_div_frac_accurate(const hal_utils_clk_info_t *clk_in
// Carry bit if the decimal is greater than 1.0 - 1.0 / ((max_fract - 1) * 2)
if (freq_error < clk_info->exp_freq_hz - clk_info->exp_freq_hz / (clk_info->max_fract - 1) * 2) {
// Search the closest fraction, time complexity O(n)
for (uint32_t sub = 0, a = 2, b = 0, min = UINT32_MAX; min && a < clk_info->max_fract; a++) {
b = (a * freq_error + clk_info->exp_freq_hz / 2) / clk_info->exp_freq_hz;
sub = _sub_abs(clk_info->exp_freq_hz * b, freq_error * a);
uint64_t min = UINT64_MAX;
for (uint32_t a = 2, b = 0; min && a < clk_info->max_fract; a++) {
b = ((uint64_t)a * freq_error + clk_info->exp_freq_hz / 2) / clk_info->exp_freq_hz;
uint64_t sub = _sub_abs((uint64_t)clk_info->exp_freq_hz * b, (uint64_t)freq_error * a);
if (sub < min) {
div_denom = a;
div_numer = b;

10
components/hal/test_apps/hal_utils/main/test_calc_clk_div.c
View File

@@ -1,5 +1,5 @@
/*
* SPDX-FileCopyrightText: 2023 Espressif Systems (Shanghai) CO LTD
* SPDX-FileCopyrightText: 2023-2026 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
@@ -80,6 +80,14 @@ TEST_CASE("test_fractal_division", "[clk_div]")
TEST_ASSERT_EQUAL_UINT32(9, clk_div.integer);
TEST_ASSERT_UINT32_WITHIN(clk_info.exp_freq_hz * 0.0001, clk_info.exp_freq_hz, real_freq);
// Fractional division whose intermediate products exceed UINT32_MAX
clk_info.exp_freq_hz = 42 * 1000 * 1000 + 336 * 1000;
real_freq = hal_utils_calc_clk_div_frac_accurate(&clk_info, &clk_div);
TEST_ASSERT_EQUAL_UINT32(3, clk_div.integer);
TEST_ASSERT_EQUAL_UINT32(286, clk_div.numerator);
TEST_ASSERT_EQUAL_UINT32(367, clk_div.denominator);
TEST_ASSERT_EQUAL_UINT32(42335977, real_freq);
// Fractal division with no error
clk_info.exp_freq_hz = 50 * 1000 * 1000;
real_freq = hal_utils_calc_clk_div_frac_fast(&clk_info, &clk_div);