From 6987aca1ce27d8ff9080f9fd60854a8c54eb0b10 Mon Sep 17 00:00:00 2001
From: Song Ruo Jing <songruojing@espressif.com>
Date: Mon, 26 Jan 2026 19:03:30 +0800
Subject: [PATCH] fix(ledc): prevent potential underflow causes multi-fade
 param calculation errors

Closes https://github.com/espressif/esp-idf/issues/17980
---
 components/esp_driver_ledc/src/ledc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/components/esp_driver_ledc/src/ledc.c b/components/esp_driver_ledc/src/ledc.c
index 3a951c14e8f..e90e7a6e8ef 100644
--- a/components/esp_driver_ledc/src/ledc.c
+++ b/components/esp_driver_ledc/src/ledc.c
@@ -1828,6 +1828,10 @@ esp_err_t ledc_fill_multi_fade_param_list(ledc_mode_t speed_mode, ledc_channel_t
                 scale = LEDC_LL_DUTY_SCALE_MAX;
             }
             step = duty_delta / scale;
+            // Ensure step * cycle doesn't exceed cycles_per_phase to prevent underflow to surplus_cycles_last_phase
+            if (step > cycles_per_phase) {
+                step = cycles_per_phase;
+            }
         }
 
         // Prepare for next phase calculation