ledc: Channel configuration requires the ledc core clock on to be effective. Therefore, a clock source is selected for the core clock since the peripheral initialization. Additionally, correct the usage of channel para_up and duty_start bits.

components/driver/ledc.c

@@ -258,7 +258,6 @@ int duty_val, ledc_duty_direction_t duty_direction, uint32_t duty_num, uint32_t
     ledc_hal_set_duty_range(&(p_ledc_obj[speed_mode]->ledc_hal), channel, 0);
     ledc_hal_set_range_number(&(p_ledc_obj[speed_mode]->ledc_hal), channel, 1);
 #endif
-    ledc_ls_channel_update(speed_mode, channel);
     return ESP_OK;
 }
 
@@ -662,6 +661,13 @@ esp_err_t ledc_channel_config(const ledc_channel_config_t *ledc_conf)
             return ESP_ERR_NO_MEM;
         }
         ledc_hal_init(&(p_ledc_obj[speed_mode]->ledc_hal), speed_mode);
+#if !CONFIG_IDF_TARGET_ESP32
+        // On targets other than esp32, the default ledc core(global) clock does not connect to any clock source
+        // Set channel configurations and update bits before core clock is on could lead to error
+        // Therefore, we should connect the core clock to a real clock source to make it on before any ledc register operation
+        // It can be switched to the other desired clock sources to meet the output pwm freq requirement later at timer configuration
+        ledc_hal_set_slow_clk_sel(&(p_ledc_obj[speed_mode]->ledc_hal), 1);
+#endif
     }
 
     /*set channel parameters*/
@@ -940,6 +946,7 @@ void IRAM_ATTR ledc_fade_isr(void *arg)
                                  scale);
                 s_ledc_fade_rec[speed_mode][channel]->fsm = LEDC_FSM_HW_FADE;
                 ledc_hal_set_duty_start(&(p_ledc_obj[speed_mode]->ledc_hal), channel, true);
+                ledc_ls_channel_update(speed_mode, channel);
             }
             portEXIT_CRITICAL_ISR(&ledc_spinlock);
             if (finished) {

components/hal/esp32c6/include/hal/ledc_ll.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2022 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2022-2023 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */

components/hal/ledc_hal.c

@@ -9,6 +9,7 @@
 #include "esp_attr.h"
 #include "hal/ledc_hal.h"
 #include "soc/soc_caps.h"
+#include "sdkconfig.h"
 #include "hal/assert.h"
 
 void ledc_hal_init(ledc_hal_context_t *hal, ledc_mode_t speed_mode)

docs/en/api-reference/peripherals/ledc.rst

@@ -42,6 +42,10 @@ As an optional step, it is also possible to set up an interrupt on fade end.
 
     Key Settings of LED PWM Controller's API
 
+.. note::
+
+    For an initial setup, it is recommended to configure for the timers first (by calling :cpp:func:`ledc_timer_config`), and then for the channels (by calling :cpp:func:`ledc_channel_config`). This ensures the PWM frequency is at the desired value since the appearance of the PWM signal from the IO pad.
+
 
 .. _ledc-api-configure-timer:
 

docs/zh_CN/api-reference/peripherals/ledc.rst

@@ -42,6 +42,10 @@ LED PWM 控制器可在无需 CPU 干预的情况下自动改变占空比，实
 
     LED PWM 控制器 API 的关键配置
 
+.. note::
+
+    首次 LEDC 配置时，建议先配置定时器（调用函数 :cpp:func:`ledc_timer_config`），再配置通道（调用函数 :cpp:func:`ledc_channel_config`）。这样可以确保 IO 脚上的 PWM 信号自有输出开始其频率就是正确的。
+
 
 .. _ledc-api-configure-timer: