fix(ledc): left-off gamma ram registers should be cleared

Hardware reads in (range_number+1) fade parameter registers, which could
cause output waveform error.

components/driver/ledc/ledc.c

@@ -212,6 +212,8 @@ int duty_val, ledc_duty_direction_t duty_direction, uint32_t duty_num, uint32_t
 #if SOC_LEDC_GAMMA_CURVE_FADE_SUPPORTED
     ledc_hal_set_duty_range_wr_addr(&(p_ledc_obj[speed_mode]->ledc_hal), channel, 0);
     ledc_hal_set_range_number(&(p_ledc_obj[speed_mode]->ledc_hal), channel, 1);
+    // Clear left-off LEDC gamma ram registers, random data in ram could cause output waveform error
+    ledc_hal_clear_left_off_fade_param(&(p_ledc_obj[speed_mode]->ledc_hal), channel, 1);
 #endif
     return ESP_OK;
 }
@@ -1274,6 +1276,8 @@ static esp_err_t _ledc_set_multi_fade(ledc_mode_t speed_mode, ledc_channel_t cha
         ledc_hal_set_duty_range_wr_addr(&(p_ledc_obj[speed_mode]->ledc_hal), channel, i);
     }
     ledc_hal_set_range_number(&(p_ledc_obj[speed_mode]->ledc_hal), channel, list_len);
+    // Clear left-off LEDC gamma ram registers, random data in ram could cause output waveform error
+    ledc_hal_clear_left_off_fade_param(&(p_ledc_obj[speed_mode]->ledc_hal), channel, list_len);
     portEXIT_CRITICAL(&ledc_spinlock);
     // Calculate target duty, and take account for overflow
     uint32_t target_duty = start_duty;

components/hal/include/hal/ledc_hal.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2019-2022 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2019-2024 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -386,6 +386,15 @@ void ledc_hal_get_range_number(ledc_hal_context_t *hal, ledc_channel_t channel_n
  * @return None
  */
 void ledc_hal_get_fade_param(ledc_hal_context_t *hal, ledc_channel_t channel_num, uint32_t range, uint32_t *dir, uint32_t *cycle, uint32_t *scale, uint32_t *step);
+
+/**
+ * @brief Clear left-off range fade parameters in LEDC gamma ram
+ *
+ * @param hal Context of the HAL layer
+ * @param channel_num LEDC channel index, select from ledc_channel_t
+ * @param start_range Start of the range to clear
+ */
+void ledc_hal_clear_left_off_fade_param(ledc_hal_context_t *hal, ledc_channel_t channel_num, uint32_t start_range);
 #endif //SOC_LEDC_GAMMA_CURVE_FADE_SUPPORTED
 
 /**

components/hal/ledc_hal_iram.c

@@ -1,11 +1,11 @@
 /*
- * SPDX-FileCopyrightText: 2019-2022 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2019-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
 
 // The HAL layer for LEDC (common part, in iram)
-// make these functions in a seperate file to make sure all LL functions are in the IRAM.
+// make these functions in a separate file to make sure all LL functions are in the IRAM.
 
 #include "esp_attr.h"
 #include "hal/ledc_hal.h"
@@ -70,6 +70,17 @@ void ledc_hal_get_range_number(ledc_hal_context_t *hal, ledc_channel_t channel_n
 {
     ledc_ll_get_range_number(hal->dev, hal->speed_mode, channel_num, range_num);
 }
+
+void ledc_hal_clear_left_off_fade_param(ledc_hal_context_t *hal, ledc_channel_t channel_num, uint32_t start_range)
+{
+    for (int i = start_range; i < SOC_LEDC_GAMMA_CURVE_FADE_RANGE_MAX; i++) {
+        ledc_ll_set_duty_direction(hal->dev, hal->speed_mode, channel_num, 0);
+        ledc_ll_set_duty_cycle(hal->dev, hal->speed_mode, channel_num, 0);
+        ledc_ll_set_duty_scale(hal->dev, hal->speed_mode, channel_num, 0);
+        ledc_ll_set_duty_num(hal->dev, hal->speed_mode, channel_num, 0);
+        ledc_ll_set_duty_range_wr_addr(hal->dev, hal->speed_mode, channel_num, i);
+    }
+}
 #endif //SOC_LEDC_GAMMA_CURVE_FADE_SUPPORTED
 
 void ledc_hal_get_fade_end_intr_status(ledc_hal_context_t *hal, uint32_t *intr_status)