stm32/eth: Add low-power mode configuration option.

Add low power functionality configurable with:

    lan.config(low_power=True/False)

ports/stm32/eth.c

@@ -46,6 +46,7 @@
 #define PHY_BCR                 (0x0000)
 #define PHY_BCR_SOFT_RESET      (0x8000)
 #define PHY_BCR_AUTONEG_EN      (0x1000)
+#define PHY_BCR_POWER_DOWN      (0x0800U)
 
 #undef PHY_BSR
 #define PHY_BSR                 (0x0001)
@@ -188,17 +189,6 @@ STATIC uint32_t eth_phy_read(uint32_t reg) {
 void eth_init(eth_t *self, int mac_idx) {
     mp_hal_get_mac(mac_idx, &self->netif.hwaddr[0]);
     self->netif.hwaddr_len = 6;
-}
-
-void eth_set_trace(eth_t *self, uint32_t value) {
-    self->trace_flags = value;
-}
-
-STATIC int eth_mac_init(eth_t *self) {
-    // Configure MPU
-    uint32_t irq_state = mpu_config_start();
-    mpu_config_region(MPU_REGION_ETH, (uint32_t)&eth_dma, MPU_CONFIG_ETH(MPU_REGION_SIZE_16KB));
-    mpu_config_end(irq_state);
 
     // Configure GPIO
     mp_hal_pin_config_alt_static(MICROPY_HW_ETH_MDC, MP_HAL_PIN_MODE_ALT, MP_HAL_PIN_PULL_NONE, STATIC_AF_ETH_MDC);
@@ -211,6 +201,27 @@ STATIC int eth_mac_init(eth_t *self) {
     mp_hal_pin_config_alt_static(MICROPY_HW_ETH_RMII_TXD0, MP_HAL_PIN_MODE_ALT, MP_HAL_PIN_PULL_NONE, STATIC_AF_ETH_RMII_TXD0);
     mp_hal_pin_config_alt_static(MICROPY_HW_ETH_RMII_TXD1, MP_HAL_PIN_MODE_ALT, MP_HAL_PIN_PULL_NONE, STATIC_AF_ETH_RMII_TXD1);
 
+    // Enable peripheral clock
+    #if defined(STM32H7)
+    __HAL_RCC_ETH1MAC_CLK_ENABLE();
+    __HAL_RCC_ETH1TX_CLK_ENABLE();
+    __HAL_RCC_ETH1RX_CLK_ENABLE();
+    #else
+    __HAL_RCC_ETH_CLK_ENABLE();
+    #endif
+}
+
+void eth_set_trace(eth_t *self, uint32_t value) {
+    self->trace_flags = value;
+}
+
+STATIC int eth_mac_init(eth_t *self) {
+    // Configure MPU
+    uint32_t irq_state = mpu_config_start();
+    mpu_config_region(MPU_REGION_ETH, (uint32_t)&eth_dma, MPU_CONFIG_ETH(MPU_REGION_SIZE_16KB));
+    mpu_config_end(irq_state);
+
+    // Enable peripheral clock
     #if defined(STM32H7)
     __HAL_RCC_ETH1MAC_CLK_ENABLE();
     __HAL_RCC_ETH1TX_CLK_ENABLE();
@@ -791,6 +802,10 @@ int eth_link_status(eth_t *self) {
 
 int eth_start(eth_t *self) {
     eth_lwip_deinit(self);
+
+    // Make sure Eth is Not in low power mode.
+    eth_low_power_mode(self, false);
+
     int ret = eth_mac_init(self);
     if (ret < 0) {
         return ret;
@@ -805,4 +820,29 @@ int eth_stop(eth_t *self) {
     return 0;
 }
 
+void eth_low_power_mode(eth_t *self, bool enable) {
+    (void)self;
+
+    // Enable eth clock
+    #if defined(STM32H7)
+    __HAL_RCC_ETH1MAC_CLK_ENABLE();
+    #else
+    __HAL_RCC_ETH_CLK_ENABLE();
+    #endif
+
+    uint16_t bcr = eth_phy_read(PHY_BCR);
+    if (enable) {
+        // Enable low-power mode.
+        eth_phy_write(PHY_BCR, bcr | PHY_BCR_POWER_DOWN);
+        // Disable eth clock.
+        #if defined(STM32H7)
+        __HAL_RCC_ETH1MAC_CLK_DISABLE();
+        #else
+        __HAL_RCC_ETH_CLK_DISABLE();
+        #endif
+    } else {
+        // Disable low-power mode.
+        eth_phy_write(PHY_BCR, bcr & (~PHY_BCR_POWER_DOWN));
+    }
+}
 #endif // defined(MICROPY_HW_ETH_MDC)

ports/stm32/eth.h

@@ -35,5 +35,6 @@ struct netif *eth_netif(eth_t *self);
 int eth_link_status(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);
 
 #endif // MICROPY_INCLUDED_STM32_ETH_H

ports/stm32/network_lan.c

@@ -134,6 +134,10 @@ STATIC mp_obj_t network_lan_config(size_t n_args, const mp_obj_t *args, mp_map_t
                         eth_set_trace(self->eth, mp_obj_get_int(e->value));
                         break;
                     }
+                    case MP_QSTR_low_power: {
+                        eth_low_power_mode(self->eth, mp_obj_get_int(e->value));
+                        break;
+                    }
                     default:
                         mp_raise_ValueError(MP_ERROR_TEXT("unknown config param"));
                 }