diff --git a/drivers/net/ethernet/sfc/mcdi.c b/drivers/net/ethernet/sfc/mcdi.c
index dffadb2..4f3301d 100644
--- a/drivers/net/ethernet/sfc/mcdi.c
+++ b/drivers/net/ethernet/sfc/mcdi.c
@@ -105,16 +105,39 @@
 	efx->type->mcdi_read_response(efx, outbuf, 4, outlen);
 }
 
+static int efx_mcdi_errno(unsigned int mcdi_err)
+{
+	switch (mcdi_err) {
+	case 0:
+		return 0;
+#define TRANSLATE_ERROR(name)					\
+	case MC_CMD_ERR_ ## name:				\
+		return -name;
+	TRANSLATE_ERROR(ENOENT);
+	TRANSLATE_ERROR(EINTR);
+	TRANSLATE_ERROR(EACCES);
+	TRANSLATE_ERROR(EBUSY);
+	TRANSLATE_ERROR(EINVAL);
+	TRANSLATE_ERROR(EDEADLK);
+	TRANSLATE_ERROR(ENOSYS);
+	TRANSLATE_ERROR(ETIME);
+#undef TRANSLATE_ERROR
+	default:
+		return -EIO;
+	}
+}
+
 static int efx_mcdi_poll(struct efx_nic *efx)
 {
 	struct efx_mcdi_iface *mcdi = efx_mcdi(efx);
 	unsigned long time, finish;
 	unsigned int respseq, respcmd, error;
-	unsigned int rc, spins;
+	unsigned int spins;
 	efx_dword_t reg;
+	int rc;
 
 	/* Check for a reboot atomically with respect to efx_mcdi_copyout() */
-	rc = -efx_mcdi_poll_reboot(efx);
+	rc = efx_mcdi_poll_reboot(efx);
 	if (rc)
 		goto out;
 
@@ -151,32 +174,15 @@
 
 	if (error && mcdi->resplen == 0) {
 		netif_err(efx, hw, efx->net_dev, "MC rebooted\n");
-		rc = EIO;
+		rc = -EIO;
 	} else if ((respseq ^ mcdi->seqno) & SEQ_MASK) {
 		netif_err(efx, hw, efx->net_dev,
 			  "MC response mismatch tx seq 0x%x rx seq 0x%x\n",
 			  respseq, mcdi->seqno);
-		rc = EIO;
+		rc = -EIO;
 	} else if (error) {
 		efx->type->mcdi_read_response(efx, &reg, 4, 4);
-		switch (EFX_DWORD_FIELD(reg, EFX_DWORD_0)) {
-#define TRANSLATE_ERROR(name)					\
-		case MC_CMD_ERR_ ## name:			\
-			rc = name;				\
-			break
-			TRANSLATE_ERROR(ENOENT);
-			TRANSLATE_ERROR(EINTR);
-			TRANSLATE_ERROR(EACCES);
-			TRANSLATE_ERROR(EBUSY);
-			TRANSLATE_ERROR(EINVAL);
-			TRANSLATE_ERROR(EDEADLK);
-			TRANSLATE_ERROR(ENOSYS);
-			TRANSLATE_ERROR(ETIME);
-#undef TRANSLATE_ERROR
-		default:
-			rc = EIO;
-			break;
-		}
+		rc = efx_mcdi_errno(EFX_DWORD_FIELD(reg, EFX_DWORD_0));
 	} else
 		rc = 0;
 
@@ -271,7 +277,7 @@
 }
 
 static void efx_mcdi_ev_cpl(struct efx_nic *efx, unsigned int seqno,
-			    unsigned int datalen, unsigned int errno)
+			    unsigned int datalen, unsigned int mcdi_err)
 {
 	struct efx_mcdi_iface *mcdi = efx_mcdi(efx);
 	bool wake = false;
@@ -287,7 +293,7 @@
 				  "MC response mismatch tx seq 0x%x rx "
 				  "seq 0x%x\n", seqno, mcdi->seqno);
 	} else {
-		mcdi->resprc = errno;
+		mcdi->resprc = efx_mcdi_errno(mcdi_err);
 		mcdi->resplen = datalen;
 
 		wake = true;
@@ -357,10 +363,12 @@
 		 * a spurious efx_mcdi_ev_cpl() running concurrently by
 		 * acquiring the iface_lock. */
 		spin_lock_bh(&mcdi->iface_lock);
-		rc = -mcdi->resprc;
+		rc = mcdi->resprc;
 		resplen = mcdi->resplen;
 		spin_unlock_bh(&mcdi->iface_lock);
 
+		BUG_ON(rc > 0);
+
 		if (rc == 0) {
 			efx_mcdi_copyout(efx, outbuf,
 					 min(outlen, mcdi->resplen));
@@ -491,7 +499,7 @@
 	case MCDI_EVENT_CODE_BADSSERT:
 		netif_err(efx, hw, efx->net_dev,
 			  "MC watchdog or assertion failure at 0x%x\n", data);
-		efx_mcdi_ev_death(efx, EINTR);
+		efx_mcdi_ev_death(efx, -EINTR);
 		break;
 
 	case MCDI_EVENT_CODE_PMNOTICE:
@@ -517,7 +525,7 @@
 		break;
 	case MCDI_EVENT_CODE_REBOOT:
 		netif_info(efx, hw, efx->net_dev, "MC Reboot\n");
-		efx_mcdi_ev_death(efx, EIO);
+		efx_mcdi_ev_death(efx, -EIO);
 		break;
 	case MCDI_EVENT_CODE_MAC_STATS_DMA:
 		/* MAC stats are gather lazily.  We can ignore this. */