stm32/eth: Add link state detection and fix active() method.

This implements automatic detection of Ethernet cable connect/disconnect
events and fixes the active() method to return interface state instead
of link state.

Changes:
- Add PHY interrupt register support and link tracking in eth_t
- Implement periodic PHY link status polling in ETH_IRQHandler
- Update LWIP netif link state based on cable connection
- Add enabled flag to track interface state vs physical link
- Fix active() to return eth_is_enabled() instead of link status
- Trigger DHCP renewal when link comes back up

The implementation polls link status every ~100 RX interrupts,
providing good responsiveness while minimizing overhead. The active()
method now correctly reflects whether the interface has been explicitly
enabled/disabled by the user, independent of cable state.

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

Author: pi-anl

ports/stm32/eth.c

@@ -119,6 +119,8 @@ typedef struct _eth_t {
     struct dhcp dhcp_struct;
     uint32_t phy_addr;
     int16_t (*phy_get_link_status)(uint32_t phy_addr);
+    bool last_link_status;
+    bool enabled;
 } eth_t;
 
 static eth_dma_t eth_dma MICROPY_HW_ETH_DMA_ATTRIBUTE;
@@ -188,6 +190,8 @@ int eth_init(eth_t *self, int mac_idx, uint32_t phy_addr, int phy_type) {
     mp_hal_get_mac(mac_idx, &self->netif.hwaddr[0]);
     self->netif.hwaddr_len = 6;
     self->phy_addr = phy_addr;
+    self->last_link_status = false;
+    self->enabled = false;
     if (phy_type == ETH_PHY_DP83825 || phy_type == ETH_PHY_DP83848) {
         self->phy_get_link_status = eth_phy_dp838xx_get_link_status;
     } else if (phy_type == ETH_PHY_LAN8720 || phy_type == ETH_PHY_LAN8742) {
@@ -396,6 +400,13 @@ static int eth_mac_init(eth_t *self) {
     // Get register with link status
     uint16_t phy_scsr = self->phy_get_link_status(self->phy_addr);
 
+    // Initialize link status tracking
+    uint16_t bsr = eth_phy_read(self->phy_addr, PHY_BSR);
+    self->last_link_status = (bsr & PHY_BSR_LINK_STATUS) != 0;
+
+    // Enable PHY link change interrupts (for future use if PHY interrupt pin available)
+    eth_phy_enable_link_interrupts(self->phy_addr);
+
     // Burst mode configuration
     #if defined(STM32H5) || defined(STM32H7)
     ETH->DMASBMR = ETH->DMASBMR & ~ETH_DMASBMR_AAL & ~ETH_DMASBMR_FB;
@@ -713,6 +724,36 @@ void ETH_IRQHandler(void) {
             eth_dma_rx_free();
         }
     }
+
+    // Check for PHY link status changes (polled approach)
+    // This runs on every RX interrupt, providing reasonable responsiveness
+    static uint32_t link_check_counter = 0;
+    if (++link_check_counter >= 100) { // Check every ~100 RX interrupts
+        link_check_counter = 0;
+
+        // Read current PHY link status
+        uint16_t bsr = eth_phy_read(eth_instance.phy_addr, PHY_BSR);
+        bool current_link_status = (bsr & PHY_BSR_LINK_STATUS) != 0;
+
+        // Check if link status changed
+        if (current_link_status != eth_instance.last_link_status) {
+            eth_instance.last_link_status = current_link_status;
+
+            // Update LWIP netif link status to reflect physical cable connection
+            struct netif *netif = &eth_instance.netif;
+            if (current_link_status) {
+                // Cable is physically connected
+                netif_set_link_up(netif);
+                // Restart DHCP if interface is up and DHCP is enabled
+                if (netif_is_up(netif) && netif_dhcp_data(netif)) {
+                    dhcp_renew(netif);
+                }
+            } else {
+                // Cable is physically disconnected
+                netif_set_link_down(netif);
+            }
+        }
+    }
 }
 
 /*******************************************************************************/
@@ -849,6 +890,10 @@ int eth_link_status(eth_t *self) {
     }
 }
 
+bool eth_is_enabled(eth_t *self) {
+    return self->enabled;
+}
+
 int eth_start(eth_t *self) {
     eth_lwip_deinit(self);
 
@@ -860,12 +905,14 @@ int eth_start(eth_t *self) {
         return ret;
     }
     eth_lwip_init(self);
+    self->enabled = true;
     return 0;
 }
 
 int eth_stop(eth_t *self) {
     eth_lwip_deinit(self);
     eth_mac_deinit(self);
+    self->enabled = false;
     return 0;
 }
 

ports/stm32/eth.h

@@ -40,6 +40,7 @@ int eth_init(eth_t *self, int mac_idx, uint32_t phy_addr, int phy_type);
 void eth_set_trace(eth_t *self, uint32_t value);
 struct netif *eth_netif(eth_t *self);
 int eth_link_status(eth_t *self);
+bool eth_is_enabled(eth_t *self);
 int eth_start(eth_t *self);
 int eth_stop(eth_t *self);
 void eth_low_power_mode(eth_t *self, bool enable);

ports/stm32/eth_phy.h

@@ -56,6 +56,7 @@
 #define PHY_SPEED_100FULL  (6)
 #define PHY_DUPLEX         (4)
 
+
 uint32_t eth_phy_read(uint32_t phy_addr, uint32_t reg);
 void eth_phy_write(uint32_t phy_addr, uint32_t reg, uint32_t val);
 

ports/stm32/network_lan.c

@@ -73,7 +73,7 @@ static mp_obj_t network_lan_make_new(const mp_obj_type_t *type, size_t n_args, s
 static mp_obj_t network_lan_active(size_t n_args, const mp_obj_t *args) {
     network_lan_obj_t *self = MP_OBJ_TO_PTR(args[0]);
     if (n_args == 1) {
-        return mp_obj_new_bool(eth_link_status(self->eth));
+        return mp_obj_new_bool(eth_is_enabled(self->eth));
     } else {
         int ret;
         if (mp_obj_is_true(args[1])) {