From 90c10103b81fd705b5581b4491e853137d2d914b Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Sat, 14 Mar 2026 17:08:42 -1000
Subject: [PATCH] [ethernet] Throttle RP2040 link polling, fix defines.h
 warnings

- Throttle linkStatus()/connected() polling to 500ms intervals to
  avoid excessive SPI transactions on every loop iteration
- Guard USE_ETHERNET/USE_ETHERNET_SPI in RP2040 defines.h block
  with #ifndef to prevent macro redefinition warnings
---
 esphome/components/ethernet/ethernet_component.h     |  2 ++
 .../ethernet/ethernet_component_rp2040.cpp           | 12 +++++++-----
 esphome/core/defines.h                               |  4 ++++
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/esphome/components/ethernet/ethernet_component.h b/esphome/components/ethernet/ethernet_component.h
index ad2368e03fe..7c139bb19c1 100644
--- a/esphome/components/ethernet/ethernet_component.h
+++ b/esphome/components/ethernet/ethernet_component.h
@@ -214,7 +214,9 @@ class EthernetComponent : public Component {
 #endif  // USE_ESP32
 
 #ifdef USE_RP2040
+  static constexpr uint32_t LINK_CHECK_INTERVAL = 500;  // ms between link/IP polls
   Wiznet5500lwIP *eth_{nullptr};
+  uint32_t last_link_check_{0};
   uint8_t clk_pin_;
   uint8_t miso_pin_;
   uint8_t mosi_pin_;
diff --git a/esphome/components/ethernet/ethernet_component_rp2040.cpp b/esphome/components/ethernet/ethernet_component_rp2040.cpp
index fd2ff4a6473..c4f7aceac8e 100644
--- a/esphome/components/ethernet/ethernet_component_rp2040.cpp
+++ b/esphome/components/ethernet/ethernet_component_rp2040.cpp
@@ -81,11 +81,15 @@ void EthernetComponent::setup() {
 
 void EthernetComponent::loop() {
   // On RP2040, we need to poll connection state since there are no events.
-  // linkStatus() reads the W5500 PHY register via SPI — no lwip state involved.
+  const uint32_t now = App.get_loop_component_start_time();
+
+  // Throttle link/IP polling to avoid excessive SPI transactions from linkStatus()
+  // which reads the W5500 PHY register via SPI on every call.
   // connected() reads netif->ip_addr without LwIPLock, but this is a single
   // 32-bit aligned read (atomic on ARM) — worst case is a one-iteration-stale
   // value, which is benign for polling.
-  if (this->eth_ != nullptr) {
+  if (this->eth_ != nullptr && now - this->last_link_check_ >= LINK_CHECK_INTERVAL) {
+    this->last_link_check_ = now;
     bool link_up = this->eth_->linkStatus() == LinkON;
     bool has_ip = this->eth_->connected();
 
@@ -108,9 +112,7 @@ void EthernetComponent::loop() {
     }
   }
 
-  // Call common state machine
-  const uint32_t now = App.get_loop_component_start_time();
-
+  // State machine
   switch (this->state_) {
     case EthernetComponentState::STOPPED:
       if (this->started_) {
diff --git a/esphome/core/defines.h b/esphome/core/defines.h
index b7a298eab6d..7b234be2c4c 100644
--- a/esphome/core/defines.h
+++ b/esphome/core/defines.h
@@ -351,9 +351,13 @@
 #define USE_SOCKET_IMPL_LWIP_TCP
 #define USE_RP2040_BLE
 #define USE_SPI
+#ifndef USE_ETHERNET
 #define USE_ETHERNET
+#endif
+#ifndef USE_ETHERNET_SPI
 #define USE_ETHERNET_SPI
 #endif
+#endif
 
 #ifdef USE_LIBRETINY
 #define USE_CAPTIVE_PORTAL