esp-idf/components/hal/lcd_hal.c

70 lines
1.9 KiB
C

/*
* SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
#include "hal/lcd_hal.h"
#include "hal/lcd_ll.h"
#include "hal/log.h"
void lcd_hal_init(lcd_hal_context_t *hal, int id)
{
hal->dev = LCD_LL_GET_HW(id);
}
/**
* @brief helper function, calculate the Greatest Common Divisor
* @note gcd(a, b) = gcd(b, a % b)
* @param a bigger value
* @param b smaller value
* @return result of gcd(a, b)
*/
__attribute__((always_inline))
static inline uint32_t _gcd(uint32_t a, uint32_t b)
{
uint32_t c = a % b;
while (c != 0) {
a = b;
b = c;
c = a % b;
}
return b;
}
uint32_t lcd_hal_cal_pclk_freq(lcd_hal_context_t *hal, uint32_t src_freq_hz, uint32_t expect_pclk_freq_hz, int lcd_clk_flags)
{
// lcd_clk = module_clock_src / (n + b / a)
// pixel_clk = lcd_clk / mo
uint32_t mo = src_freq_hz / expect_pclk_freq_hz / LCD_LL_CLK_FRAC_DIV_N_MAX + 1;
if (mo == 1 && !(lcd_clk_flags & LCD_HAL_PCLK_FLAG_ALLOW_EQUAL_SYSCLK)) {
mo = 2;
}
uint32_t n = src_freq_hz / expect_pclk_freq_hz / mo;
uint32_t a = 0;
uint32_t b = 0;
// delta_hz / expect_pclk_freq_hz <==> b / a
uint32_t delta_hz = src_freq_hz / mo - expect_pclk_freq_hz * n;
// fractional divider
if (delta_hz) {
uint32_t gcd = _gcd(expect_pclk_freq_hz, delta_hz);
a = expect_pclk_freq_hz / gcd;
b = delta_hz / gcd;
// normalize div_a and div_b
uint32_t d = a / LCD_LL_CLK_FRAC_DIV_AB_MAX + 1;
a /= d;
b /= d;
}
HAL_EARLY_LOGD("lcd_hal", "n=%d,a=%d,b=%d,mo=%d", n, a, b, mo);
lcd_ll_set_group_clock_coeff(hal->dev, n, a, b);
lcd_ll_set_pixel_clock_prescale(hal->dev, mo);
if (delta_hz) {
return ((uint64_t)src_freq_hz * a) / (n * a + b) / mo;
} else {
return src_freq_hz / n / mo;
}
}