Index: head/sys/dev/sfxge/common/efx_mcdi.h
===================================================================
--- head/sys/dev/sfxge/common/efx_mcdi.h
+++ head/sys/dev/sfxge/common/efx_mcdi.h
@@ -69,6 +69,7 @@
 
 typedef struct efx_mcdi_iface_s {
 	unsigned int		emi_port;
+	unsigned int		emi_max_version;
 	unsigned int		emi_seq;
 	efx_mcdi_req_t		*emi_pending_req;
 	boolean_t		emi_ev_cpl;
Index: head/sys/dev/sfxge/common/efx_mcdi.c
===================================================================
--- head/sys/dev/sfxge/common/efx_mcdi.c
+++ head/sys/dev/sfxge/common/efx_mcdi.c
@@ -643,7 +643,6 @@
 	efx_mcdi_iface_t *emip = &(enp->en_mcdi.em_emip);
 	const efx_mcdi_transport_t *emtp = enp->en_mcdi.em_emtp;
 	efx_mcdi_ops_t *emcop = enp->en_mcdi.em_emcop;
-	efx_nic_cfg_t *encp = &enp->en_nic_cfg;
 	efx_mcdi_req_t *emrp;
 	int state;
 
@@ -668,7 +667,7 @@
 	emip->emi_pending_req = NULL;
 	EFSYS_UNLOCK(enp->en_eslp, state);
 
-	if (encp->enc_mcdi_max_payload_length > MCDI_CTL_SDU_LEN_MAX_V1) {
+	if (emip->emi_max_version >= 2) {
 		/* MCDIv2 response details do not fit into an event. */
 		efx_mcdi_read_response_header(enp, emrp);
 	} else {
Index: head/sys/dev/sfxge/common/hunt_mcdi.c
===================================================================
--- head/sys/dev/sfxge/common/hunt_mcdi.c
+++ head/sys/dev/sfxge/common/hunt_mcdi.c
@@ -81,6 +81,7 @@
 	__in		efx_nic_t *enp,
 	__in		const efx_mcdi_transport_t *emtp)
 {
+	efx_mcdi_iface_t *emip = &(enp->en_mcdi.em_emip);
 	efsys_mem_t *esmp = emtp->emt_dma_mem;
 	efx_dword_t dword;
 	efx_rc_t rc;
@@ -89,6 +90,13 @@
 		    enp->en_family == EFX_FAMILY_MEDFORD);
 	EFSYS_ASSERT(enp->en_features & EFX_FEATURE_MCDI_DMA);
 
+	/*
+	 * All EF10 firmware supports MCDIv2 and MCDIv1.
+	 * Medford BootROM supports MCDIv2 and MCDIv1.
+	 * Huntington BootROM supports MCDIv1 only.
+	 */
+	emip->emi_max_version = 2;
+
 	/* A host DMA buffer is required for EF10 MCDI */
 	if (esmp == NULL) {
 		rc = EINVAL;
Index: head/sys/dev/sfxge/common/siena_mcdi.c
===================================================================
--- head/sys/dev/sfxge/common/siena_mcdi.c
+++ head/sys/dev/sfxge/common/siena_mcdi.c
@@ -244,6 +244,9 @@
 		goto fail1;
 	}
 
+	/* Siena BootROM and firmware only support MCDIv1 */
+	emip->emi_max_version = 1;
+
 	/*
 	 * Wipe the atomic reboot status so subsequent MCDI requests succeed.
 	 * BOOT_STATUS is preserved so eno_nic_probe() can boot out of the