net: stmmac: don't overwrite discard_frame status

[ Upstream commit 1b746ce8b397e58f9e40ce5c63b7198de6930482 ]

If we have error bits set, the discard_frame status will get overwritten
by checksum bit checks, which might set the status back to good one.
Fix by checking the COE status only if the frame is good.
Signed-off-by: NAaro Koskinen <aaro.koskinen@nokia.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/net/ethernet/stmicro/stmmac/enh_desc.c

@@ -231,6 +231,7 @@ static int enh_desc_get_rx_status(void *data, struct stmmac_extra_stats *x,
 	 * It doesn't match with the information reported into the databook.
 	 * At any rate, we need to understand if the CSUM hw computation is ok
 	 * and report this info to the upper layers. */
+	if (likely(ret == good_frame))
 		ret = enh_desc_coe_rdes0(!!(rdes0 & RDES0_IPC_CSUM_ERROR),
 					 !!(rdes0 & RDES0_FRAME_TYPE),
 					 !!(rdes0 & ERDES0_RX_MAC_ADDR));