e1000: Corrections for lem(4)/em(4) txcsum offload

Explicitly set ipcss/ipcse/ipcso for IPv6 per intel SDM as indicated in
inline comments.

Fix and consolidate 82543/82547 hwcsum exemption.

While here rearrange and expand some commentary.

(cherry picked from commit cbcab907f8ad1a4ac38dbc574c747ac2901faa54)

2 files changed, 27 insertions, 21 deletions

diff --git a/sys/dev/e1000/em_txrx.c b/sys/dev/e1000/em_txrx.c
index 8b1d2817490f..0e433f388ac5 100644
--- a/sys/dev/e1000/em_txrx.c
+++ b/sys/dev/e1000/em_txrx.c
@@ -186,7 +186,7 @@ em_tso_setup(struct e1000_softc *sc, if_pkt_info_t pi, uint32_t *txd_upper,
 	TXD->tcp_seg_setup.fields.hdr_len = hdr_len;
 
 	/*
-	 * 8254x SDM4.0 page 45, and PCIe GbE SDM2.5 page 63
+	 * "PCI/PCI-X SDM 4.0" page 45, and "PCIe GbE SDM 2.5" page 63
 	 * - Set up basic TUCMDs
 	 * - Enable IP bit on 82544
 	 * - For others IP bit on indicates IPv4, while off indicates IPv6
@@ -212,10 +212,6 @@ em_tso_setup(struct e1000_softc *sc, if_pkt_info_t pi, uint32_t *txd_upper,
 	return (cur);
 }
 
-#define TSO_WORKAROUND 4
-#define DONT_FORCE_CTX 1
-
-
 /*********************************************************************
  *  The offload context is protocol specific (TCP/UDP) and thus
  *  only needs to be set when the protocol changes. The occasion
@@ -232,6 +228,7 @@ em_tso_setup(struct e1000_softc *sc, if_pkt_info_t pi, uint32_t *txd_upper,
  *  in turn greatly slow down performance to send small sized
  *  frames.
  **********************************************************************/
+#define DONT_FORCE_CTX 1
 
 static int
 em_transmit_checksum_setup(struct e1000_softc *sc, if_pkt_info_t pi,
@@ -271,20 +268,30 @@ em_transmit_checksum_setup(struct e1000_softc *sc, if_pkt_info_t pi,
 	}
 
 	TXD = (struct e1000_context_desc *)&txr->tx_base[cur];
+	/*
+	 * ipcss - Start offset for header checksum calculation.
+	 * ipcse - End offset for header checksum calculation.
+	 * ipcso - Offset of place to put the checksum.
+	 *
+	 * We set ipcsX values regardless of IP version to work around HW issues
+	 * and ipcse must be 0 for IPv6 per "PCIe GbE SDM 2.5" page 61.
+	 * IXSM controls whether it's inserted.
+	 */
+	TXD->lower_setup.ip_fields.ipcss = pi->ipi_ehdrlen;
+	TXD->lower_setup.ip_fields.ipcso = pi->ipi_ehdrlen +
+	    offsetof(struct ip, ip_sum);
 	if (csum_flags & CSUM_IP) {
 		*txd_upper |= E1000_TXD_POPTS_IXSM << 8;
-		/*
-		 * Start offset for header checksum calculation.
-		 * End offset for header checksum calculation.
-		 * Offset of place to put the checksum.
-		 */
-		TXD->lower_setup.ip_fields.ipcss = pi->ipi_ehdrlen;
 		TXD->lower_setup.ip_fields.ipcse = htole16(hdr_len);
-		TXD->lower_setup.ip_fields.ipcso = pi->ipi_ehdrlen +
-		    offsetof(struct ip, ip_sum);
 		cmd |= E1000_TXD_CMD_IP;
-	}
+	} else if (csum_flags & (CSUM_IP6_TCP | CSUM_IP6_UDP))
+		TXD->lower_setup.ip_fields.ipcse = htole16(0);
 
+	/*
+	 * tucss - Start offset for payload checksum calculation.
+	 * tucse - End offset for payload checksum calculation.
+	 * tucso - Offset of place to put the checksum.
+	 */
 	if (csum_flags & (CSUM_TCP | CSUM_UDP | CSUM_IP6_TCP | CSUM_IP6_UDP)) {
 		uint8_t tucso;
 
@@ -320,6 +327,8 @@ em_transmit_checksum_setup(struct e1000_softc *sc, if_pkt_info_t pi,
 	return (cur);
 }
 
+#define TSO_WORKAROUND 4 /* TSO sentinel descriptor */
+
 static int
 em_isc_txd_encap(void *arg, if_pkt_info_t pi)
 {
diff --git a/sys/dev/e1000/if_em.c b/sys/dev/e1000/if_em.c
index 6e8970ccf6f6..6ceab6be2b8a 100644
--- a/sys/dev/e1000/if_em.c
+++ b/sys/dev/e1000/if_em.c
@@ -950,15 +950,13 @@ em_if_attach_pre(if_ctx_t ctx)
 		scctx->isc_tx_csum_flags = CSUM_TCP | CSUM_UDP | CSUM_IP_TSO |
 		    CSUM_IP6_TCP | CSUM_IP6_UDP;
 
-		/* 8254x SDM4.0 page 33 - FDX requirement on these chips */
-		if (hw->mac.type == e1000_82547 || hw->mac.type == e1000_82547_rev_2)
+		/* "PCI/PCI-X SDM 4.0" page 33 (b) - FDX requirement on these chips */
+		if (hw->mac.type < e1000_82543 || hw->mac.type == e1000_82547 ||
+		    hw->mac.type == e1000_82547_rev_2)
 			scctx->isc_capenable &= ~(IFCAP_HWCSUM|IFCAP_VLAN_HWCSUM);
-
-		if (hw->mac.type < e1000_82543)
-			scctx->isc_capabilities &= ~(IFCAP_HWCSUM|IFCAP_VLAN_HWCSUM);
 		/* 82541ER doesn't do HW tagging */
 		if (hw->device_id == E1000_DEV_ID_82541ER || hw->device_id == E1000_DEV_ID_82541ER_LOM)
-			scctx->isc_capabilities &= ~IFCAP_VLAN_HWTAGGING;
+			scctx->isc_capenable &= ~IFCAP_VLAN_HWTAGGING;
 		/* INTx only */
 		scctx->isc_msix_bar = 0;
 	}
@@ -1354,7 +1352,6 @@ em_if_init(if_ctx_t ctx)
 		    E1000_RAR_ENTRIES - 1);
 	}
 
-
 	/* Initialize the hardware */
 	em_reset(ctx);
 	em_if_update_admin_status(ctx);