sfxge(4): query and use current MTU if setting the MTU fails

This allows the driver to fall back to the largest usable MTU if a
user attempts to configure an unprivileged function with an MTU higher
than that of the attached port.

Submitted by:   Mark Spender <mspender at solarflare.com>
Sponsored by:   Solarflare Communications, Inc.
MFC after:      1 week
Differential Revision:  https://reviews.freebsd.org/D6387

sys/dev/sfxge/common/ef10_impl.h

@@ -235,6 +235,11 @@ extern	__checkReturn	efx_rc_t
 ef10_mac_pdu_set(
 	__in	efx_nic_t *enp);
 
+extern	__checkReturn	efx_rc_t
+ef10_mac_pdu_get(
+	__in	efx_nic_t *enp,
+	__out	size_t *pdu);
+
 extern	__checkReturn	efx_rc_t
 ef10_mac_reconfigure(
 	__in	efx_nic_t *enp);

sys/dev/sfxge/common/ef10_mac.c

@@ -199,6 +199,53 @@ fail1:
 	return (rc);
 }
 
+static	__checkReturn		efx_rc_t
+efx_mcdi_mtu_get(
+	__in		efx_nic_t *enp,
+	__out		size_t *mtu)
+{
+	efx_mcdi_req_t req;
+	uint8_t payload[MAX(MC_CMD_SET_MAC_EXT_IN_LEN,
+			    MC_CMD_SET_MAC_V2_OUT_LEN)];
+	efx_rc_t rc;
+
+	(void) memset(payload, 0, sizeof (payload));
+	req.emr_cmd = MC_CMD_SET_MAC;
+	req.emr_in_buf = payload;
+	req.emr_in_length = MC_CMD_SET_MAC_EXT_IN_LEN;
+	req.emr_out_buf = payload;
+	req.emr_out_length = MC_CMD_SET_MAC_V2_OUT_LEN;
+
+	/*
+	 * With MC_CMD_SET_MAC_EXT_IN_CONTROL set to 0, this just queries the
+	 * MTU.  This should always be supported on Medford, but it is not
+	 * supported on older Huntington firmware.
+	 */
+	MCDI_IN_SET_DWORD(req, SET_MAC_EXT_IN_CONTROL, 0);
+
+	efx_mcdi_execute(enp, &req);
+
+	if (req.emr_rc != 0) {
+		rc = req.emr_rc;
+		goto fail1;
+	}
+	if (req.emr_out_length_used < MC_CMD_SET_MAC_V2_OUT_MTU_OFST + 4) {
+		rc = EMSGSIZE;
+		goto fail2;
+	}
+
+	*mtu = MCDI_OUT_DWORD(req, SET_MAC_V2_OUT_MTU);
+
+	return (0);
+
+fail2:
+	EFSYS_PROBE(fail2);
+fail1:
+	EFSYS_PROBE1(fail1, efx_rc_t, rc);
+
+	return (rc);
+}
+
 	__checkReturn	efx_rc_t
 ef10_mac_pdu_set(
 	__in		efx_nic_t *enp)
@@ -230,6 +277,24 @@ fail1:
 	return (rc);
 }
 
+	__checkReturn		efx_rc_t
+ef10_mac_pdu_get(
+	__in		efx_nic_t *enp,
+	__out		size_t *pdu)
+{
+	efx_rc_t rc;
+
+	if ((rc = efx_mcdi_mtu_get(enp, pdu)) != 0)
+		goto fail1;
+
+	return (0);
+
+fail1:
+	EFSYS_PROBE1(fail1, efx_rc_t, rc);
+
+	return (rc);
+}
+
 __checkReturn	efx_rc_t
 ef10_mac_reconfigure(
 	__in		efx_nic_t *enp)

sys/dev/sfxge/common/efx.h

@@ -442,17 +442,29 @@ typedef enum efx_link_mode_e {
 
 #define	EFX_MAC_SDU_MAX	9202
 
-#define	EFX_MAC_PDU(_sdu) 				\
-	P2ROUNDUP(((_sdu)				\
-		    + /* EtherII */ 14			\
-		    + /* VLAN */ 4			\
-		    + /* CRC */ 4			\
-		    + /* bug16011 */ 16),		\
-		    (1 << 3))
+#define	EFX_MAC_PDU_ADJUSTMENT					\
+	(/* EtherII */ 14					\
+	    + /* VLAN */ 4					\
+	    + /* CRC */ 4					\
+	    + /* bug16011 */ 16)				\
+
+#define	EFX_MAC_PDU(_sdu)					\
+	P2ROUNDUP((_sdu) + EFX_MAC_PDU_ADJUSTMENT, 8)
+
+/*
+ * Due to the P2ROUNDUP in EFX_MAC_PDU(), EFX_MAC_SDU_FROM_PDU() may give
+ * the SDU rounded up slightly.
+ */
+#define	EFX_MAC_SDU_FROM_PDU(_pdu)	((_pdu) - EFX_MAC_PDU_ADJUSTMENT)
 
 #define	EFX_MAC_PDU_MIN	60
 #define	EFX_MAC_PDU_MAX	EFX_MAC_PDU(EFX_MAC_SDU_MAX)
 
+extern	__checkReturn	efx_rc_t
+efx_mac_pdu_get(
+	__in		efx_nic_t *enp,
+	__out		size_t *pdu);
+
 extern	__checkReturn	efx_rc_t
 efx_mac_pdu_set(
 	__in		efx_nic_t *enp,

sys/dev/sfxge/common/efx_impl.h

@@ -183,6 +183,7 @@ typedef struct efx_mac_ops_s {
 	efx_rc_t	(*emo_up)(efx_nic_t *, boolean_t *);
 	efx_rc_t	(*emo_addr_set)(efx_nic_t *);
 	efx_rc_t	(*emo_pdu_set)(efx_nic_t *);
+	efx_rc_t	(*emo_pdu_get)(efx_nic_t *, size_t *);
 	efx_rc_t	(*emo_reconfigure)(efx_nic_t *);
 	efx_rc_t	(*emo_multicast_list_set)(efx_nic_t *);
 	efx_rc_t	(*emo_filter_default_rxq_set)(efx_nic_t *,

sys/dev/sfxge/common/efx_mac.c

@@ -48,6 +48,7 @@ static const efx_mac_ops_t	__efx_siena_mac_ops = {
 	siena_mac_up,				/* emo_up */
 	siena_mac_reconfigure,			/* emo_addr_set */
 	siena_mac_reconfigure,			/* emo_pdu_set */
+	siena_mac_pdu_get,			/* emo_pdu_get */
 	siena_mac_reconfigure,			/* emo_reconfigure */
 	siena_mac_multicast_list_set,		/* emo_multicast_list_set */
 	NULL,					/* emo_filter_set_default_rxq */
@@ -69,6 +70,7 @@ static const efx_mac_ops_t	__efx_ef10_mac_ops = {
 	ef10_mac_up,				/* emo_up */
 	ef10_mac_addr_set,			/* emo_addr_set */
 	ef10_mac_pdu_set,			/* emo_pdu_set */
+	ef10_mac_pdu_get,			/* emo_pdu_get */
 	ef10_mac_reconfigure,			/* emo_reconfigure */
 	ef10_mac_multicast_list_set,		/* emo_multicast_list_set */
 	ef10_mac_filter_default_rxq_set,	/* emo_filter_default_rxq_set */
@@ -85,7 +87,6 @@ static const efx_mac_ops_t	__efx_ef10_mac_ops = {
 };
 #endif	/* EFSYS_OPT_HUNTINGTON || EFSYS_OPT_MEDFORD */
 
-
 	__checkReturn			efx_rc_t
 efx_mac_pdu_set(
 	__in				efx_nic_t *enp,
@@ -127,6 +128,26 @@ fail2:
 fail1:
 	EFSYS_PROBE1(fail1, efx_rc_t, rc);
 
+	return (rc);
+}
+
+	__checkReturn	efx_rc_t
+efx_mac_pdu_get(
+	__in		efx_nic_t *enp,
+	__out		size_t *pdu)
+{
+	efx_port_t *epp = &(enp->en_port);
+	const efx_mac_ops_t *emop = epp->ep_emop;
+	efx_rc_t rc;
+
+	if ((rc = emop->emo_pdu_get(enp, pdu)) != 0)
+		goto fail1;
+
+	return (0);
+
+fail1:
+	EFSYS_PROBE1(fail1, efx_rc_t, rc);
+
 	return (rc);
 }
 

sys/dev/sfxge/common/siena_impl.h

@@ -388,6 +388,11 @@ extern	__checkReturn	efx_rc_t
 siena_mac_reconfigure(
 	__in	efx_nic_t *enp);
 
+extern	__checkReturn	efx_rc_t
+siena_mac_pdu_get(
+	__in	efx_nic_t *enp,
+	__out	size_t *pdu);
+
 #if EFSYS_OPT_LOOPBACK
 
 extern	__checkReturn	efx_rc_t

sys/dev/sfxge/common/siena_mac.c

@@ -432,4 +432,12 @@ siena_mac_stats_update(
 
 #endif	/* EFSYS_OPT_MAC_STATS */
 
+	__checkReturn		efx_rc_t
+siena_mac_pdu_get(
+	__in		efx_nic_t *enp,
+	__out		size_t *pdu)
+{
+	return (ENOTSUP);
+}
+
 #endif	/* EFSYS_OPT_SIENA */