drivers: ethernet: adin2111: Add calculation of EBO in OA mode

Calculate the EBO properly, so the total frame written to TX FIFO
does not exceed maximum Ethernet frame length.
Makes the TCP stack to work properly, otherwise packets > 1472 are dopped,
as they would be padded by 64 more bytes
and hence exceed maximum Ethernet frame size.

Signed-off-by: Maciej Panek <[email protected]>

Author: panekmaciej

drivers/ethernet/eth_adin2111.c

@@ -351,14 +351,25 @@ static int eth_adin2111_send_oa_frame(const struct device *dev, struct net_pkt *
 	uint16_t clen, len = net_pkt_get_len(pkt);
 	uint32_t hdr;
 	uint8_t chunks, i;
-	int ret, txc, cur;
+	int ret, txc, cur, ebo;
 
 	chunks = len / ctx->oa_cps;
 
 	if (len % ctx->oa_cps) {
 		chunks++;
 	}
 
+	if (chunks > 1) {
+		/* we have to calculate EBO so we do not exceed maximum Ethernet frame length */
+		ebo = (len % ctx->oa_cps) - 1;
+		if (ebo < 0) {
+			ebo += ctx->oa_cps;
+		}
+	} else {
+		/* we have to pad to the minimum Ethernet frame length */
+		ebo = ctx->oa_cps - 1;
+	}
+
 	ret = eth_adin2111_reg_read(dev, ADIN2111_BUFSTS, &txc);
 	if (ret < 0) {
 		LOG_ERR("Cannot read txc");
@@ -380,7 +391,7 @@ static int eth_adin2111_send_oa_frame(const struct device *dev, struct net_pkt *
 		}
 		if (i == chunks) {
 			hdr |= ADIN2111_OA_DATA_HDR_EV;
-			hdr |= (ctx->oa_cps - 1) << ADIN2111_OA_DATA_HDR_EBO;
+			hdr |= ebo << ADIN2111_OA_DATA_HDR_EBO;
 		}
 
 		hdr |= eth_adin2111_oa_get_parity(hdr);