fix(esp_eth): fix openeth driver to consider MAC address set in QEMU

Openeth driver did not consider the possibility that the MAC address
was specified when launching QEMU, and would always overwrite that
address with the address obtained from esp_read_mac.
When running QEMU, setting the MAC address via QEMU arguments is more
convenient than crafting an eFuse file with the correct MAC address.
This change modifies openeth driver to first check if an address has
been set in QEMU and uses it if so. Otherwise it falls back to the
address obtained from esp_read_mac.

As part of this change, also removed the unnecessary variable
emac_opencores_t::addr, the address is only kept in the registers of
the emulated peripheral now.

For full effect this also requires changes in QEMU, see
espressif/qemu#107 for background. Without
changes in QEMU, this commit keeps the same behavior.

components/esp_eth/src/openeth/esp_eth_mac_openeth.c

@@ -38,7 +38,6 @@ typedef struct {
     TaskHandle_t rx_task_hdl;
     int cur_rx_desc;
     int cur_tx_desc;
-    uint8_t addr[6];
     uint8_t *rx_buf[RX_BUF_COUNT];
     uint8_t *tx_buf[TX_BUF_COUNT];
 } emac_opencores_t;
@@ -143,8 +142,6 @@ static esp_err_t emac_opencores_set_addr(esp_eth_mac_t *mac, uint8_t *addr)
     ESP_LOGV(TAG, "%s: " MACSTR, __func__, MAC2STR(addr));
     esp_err_t ret = ESP_OK;
     ESP_GOTO_ON_FALSE(addr, ESP_ERR_INVALID_ARG, err, TAG, "can't set mac addr to null");
-    emac_opencores_t *emac = __containerof(mac, emac_opencores_t, parent);
-    memcpy(emac->addr, addr, 6);
     const uint8_t mac0[4] = {addr[5], addr[4], addr[3], addr[2]};
     const uint8_t mac1[4] = {addr[1], addr[0]};
     uint32_t mac0_u32, mac1_u32;
@@ -162,8 +159,17 @@ static esp_err_t emac_opencores_get_addr(esp_eth_mac_t *mac, uint8_t *addr)
     ESP_LOGV(TAG, "%s: " MACSTR, __func__, MAC2STR(addr));
     esp_err_t ret = ESP_OK;
     ESP_GOTO_ON_FALSE(addr, ESP_ERR_INVALID_ARG, err, TAG, "can't set mac addr to null");
-    emac_opencores_t *emac = __containerof(mac, emac_opencores_t, parent);
-    memcpy(addr, emac->addr, 6);
+    uint32_t mac0_u32 = REG_READ(OPENETH_MAC_ADDR0_REG);
+    uint32_t mac1_u32 = REG_READ(OPENETH_MAC_ADDR1_REG);
+    const uint8_t mac_addr[ETH_ADDR_LEN] = {
+        (mac1_u32 >> 8) & 0xFF,
+        mac1_u32 & 0xFF,
+        (mac0_u32 >> 24) & 0xFF,
+        (mac0_u32 >> 16) & 0xFF,
+        (mac0_u32 >> 8) & 0xFF,
+        mac0_u32 & 0xFF,
+    };
+    memcpy(addr, mac_addr, ETH_ADDR_LEN);
     return ESP_OK;
 err:
     return ret;
@@ -288,7 +294,6 @@ static esp_err_t emac_opencores_init(esp_eth_mac_t *mac)
     emac_opencores_t *emac = __containerof(mac, emac_opencores_t, parent);
     esp_eth_mediator_t *eth = emac->eth;
     ESP_GOTO_ON_ERROR(eth->on_state_changed(eth, ETH_STATE_LLINIT, NULL), err, TAG, "lowlevel init failed");
-    ESP_GOTO_ON_ERROR(esp_read_mac(emac->addr, ESP_MAC_ETH), err, TAG, "fetch ethernet mac address failed");
 
     // Sanity check
     if (REG_READ(OPENETH_MODER_REG) != OPENETH_MODER_DEFAULT) {
@@ -299,7 +304,19 @@ static esp_err_t emac_opencores_init(esp_eth_mac_t *mac)
     // Initialize the MAC
     openeth_reset();
     openeth_set_tx_desc_cnt(TX_BUF_COUNT);
-    emac_opencores_set_addr(mac, emac->addr);
+
+    // Check if MAC address has been set in QEMU
+    uint8_t mac_addr[ETH_ADDR_LEN];
+    emac_opencores_get_addr(mac, mac_addr);
+    const uint8_t zero_mac[ETH_ADDR_LEN] = {0};
+    if (memcmp(mac_addr, zero_mac, ETH_ADDR_LEN) != 0) {
+        ESP_LOGD(TAG, "Using MAC address " MACSTR " set in QEMU", MAC2STR(mac_addr));
+    } else {
+        // Fall back to the default MAC address
+        ESP_GOTO_ON_ERROR(esp_read_mac(mac_addr, ESP_MAC_ETH), err, TAG, "fetch ethernet mac address failed");
+        ESP_LOGD(TAG, "Using MAC address " MACSTR " from esp_read_mac", MAC2STR(mac_addr));
+        emac_opencores_set_addr(mac, mac_addr);
+    }
 
     return ESP_OK;
 err: