esp32/pwm: Use IDF functions to calculate resolution correctly.

Signed-off-by: Andrew Leech <[email protected]>

Author: pi-anl

ports/esp32/machine_pwm.c

@@ -34,6 +34,7 @@
 #include "py/mphal.h"
 #include "driver/ledc.h"
 #include "esp_err.h"
+#include "esp_clk_tree.h"
 #include "soc/gpio_sig_map.h"
 
 #define PWM_DBG(...)
@@ -209,51 +210,32 @@ static void configure_channel(machine_pwm_obj_t *self) {
 
 static void set_freq(machine_pwm_obj_t *self, unsigned int freq, ledc_timer_config_t *timer) {
     if (freq != timer->freq_hz) {
-        // Find the highest bit resolution for the requested frequency
-        unsigned int i = APB_CLK_FREQ; // 80 MHz
-        #if SOC_LEDC_SUPPORT_REF_TICK
-        if (freq < EMPIRIC_FREQ) {
-            i = REF_CLK_FREQ; // 1 MHz
-        }
-        #endif
-
-        int divider = (i + freq / 2) / freq; // rounded
-        if (divider == 0) {
-            divider = 1;
-        }
-        float f = (float)i / divider; // actual frequency
-        if (f <= 1.0) {
-            f = 1.0;
-        }
-        i = (unsigned int)roundf((float)i / f);
-
-        unsigned int res = 0;
-        for (; i > 1; i >>= 1) {
-            ++res;
-        }
-        if (res == 0) {
-            res = 1;
-        } else if (res > HIGHEST_PWM_RES) {
-            // Limit resolution to HIGHEST_PWM_RES to match units of our duty
-            res = HIGHEST_PWM_RES;
-        }
-
-        // Configure the new resolution and frequency
-        timer->duty_resolution = res;
+        // Configure the new frequency and resolution
         timer->freq_hz = freq;
-        #if SOC_LEDC_SUPPORT_XTAL_CLOCK
+
+        #if SOC_LEDC_SUPPORT_PLL_DIV_CLOCK
+        timer->clk_cfg = LEDC_USE_PLL_DIV_CLK;
+        #elif SOC_LEDC_SUPPORT_APB_CLOCK
+        timer->clk_cfg = LEDC_USE_APB_CLK;
+        #elif SOC_LEDC_SUPPORT_XTAL_CLOCK
         timer->clk_cfg = LEDC_USE_XTAL_CLK;
         #else
-        timer->clk_cfg = LEDC_USE_APB_CLK;
+        #error No supported PWM / LEDC clocks.
         #endif
         #if SOC_LEDC_SUPPORT_REF_TICK
         if (freq < EMPIRIC_FREQ) {
             timer->clk_cfg = LEDC_USE_REF_TICK;
         }
         #endif
+        uint32_t src_clk_freq = 0;
+        esp_err_t err = esp_clk_tree_src_get_freq_hz(timer->clk_cfg, ESP_CLK_TREE_SRC_FREQ_PRECISION_CACHED, &src_clk_freq);
+        if (err != ESP_OK) {
+            mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("unable to query source clock frequency %d"), (int)timer->clk_cfg);
+        }
+        timer->duty_resolution = ledc_find_suitable_duty_resolution(src_clk_freq, timer->freq_hz);
 
         // Set frequency
-        esp_err_t err = ledc_timer_config(timer);
+        err = ledc_timer_config(timer);
         if (err != ESP_OK) {
             if (err == ESP_FAIL) {
                 mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("unreachable frequency %d"), freq);