sfc: mdio_clause45_read errors go unnoticed

index f9e2f95..bcb5ddc 100644
@@ -126,23 +126,29 @@ int mdio_clause45_check_mmds(struct efx_nic *efx,
 			     unsigned int mmd_mask, unsigned int fatal_mask)
 {
 	u32 devices;
-	int mmd = 0, probe_mmd;
+	int ret, mmd = 0, probe_mmd;
 
 	/* Historically we have probed the PHYXS to find out what devices are
 	 * present,but that doesn't work so well if the PHYXS isn't expected
 	 * to exist, if so just find the first item in the list supplied. */
 	probe_mmd = (mmd_mask & MDIO_MMDREG_DEVS_PHYXS) ? MDIO_MMD_PHYXS :
 	    __ffs(mmd_mask);
-	devices = (mdio_clause45_read(efx, efx->mii.phy_id,
-				      probe_mmd, MDIO_MMDREG_DEVS0) |
-		   mdio_clause45_read(efx, efx->mii.phy_id,
-				      probe_mmd, MDIO_MMDREG_DEVS1) << 16);
 
-	/* Check all the expected MMDs are present */
-	if (devices < 0) {
+	ret = mdio_clause45_read(efx, efx->mii.phy_id, probe_mmd,
+			MDIO_MMDREG_DEVS0);
+	if (ret >= 0) {
+		devices = ret;
+		ret = mdio_clause45_read(efx, efx->mii.phy_id, probe_mmd,
+				MDIO_MMDREG_DEVS1);
+	}
+
+	/* Check all the expected MMDs were present */
+	if (ret < 0) {
 		EFX_ERR(efx, "failed to read devices present\n");
 		return -EIO;
 	}
+	devices |= ret << 16;
+
 	if ((devices & mmd_mask) != mmd_mask) {
 		EFX_ERR(efx, "required MMDs not present: got %x, "
 			"wanted %x\n", devices, mmd_mask);