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DC(4)		       FreeBSD Kernel Interfaces Manual			 DC(4)

     dc	-- DEC/Intel 21143 and clone 10/100 Ethernet driver

     To	compile	this driver into the kernel, place the following lines in your
     kernel configuration file:

	   device miibus
	   device dc

     Alternatively, to load the	driver as a module at boot time, place the
     following line in loader.conf(5):


     The dc driver provides support for	several	PCI Fast Ethernet adapters and
     embedded controllers based	on the DEC/Intel 21143 chipset and clones.

     All of supported chipsets have the	same general register layout, DMA de-
     scriptor format and method	of operation.  All of the clone	chips are
     based on the 21143	design with various modifications.  The	21143 itself
     has support for 10baseT, BNC, AUI,	MII and	symbol media attachments, 10
     and 100Mbps speeds	in full	or half	duplex,	built in NWAY autonegotiation
     and wake on LAN.  The 21143 also offers several receive filter program-
     ming options including perfect filtering, inverse perfect filtering and
     hash table	filtering.

     Some clone	chips duplicate	the 21143 fairly closely while others only
     maintain superficial similarities.	 Some support only MII media attach-
     ments.  Others use	different receiver filter programming mechanisms.  At
     least one supports	only chained DMA descriptors (most support both
     chained descriptors and contiguously allocated fixed size rings).	Some
     chips (especially the PNIC) also have peculiar bugs.  The dc driver does
     its best to provide generalized support for all of	these chipsets in or-
     der to keep special case code to a	minimum.

     These chips are used by many vendors which	makes it difficult to provide
     a complete	list of	all supported cards.

     The dc driver supports the	following media	types:

     autoselect	  Enable autoselection of the media type and options.  The
		  user can manually override the autoselected mode by adding
		  media	options	to the /etc/rc.conf file.

		  Note:	the built-in NWAY autonegotiation on the original PNIC
		  82c168 chip is horribly broken and is	not supported by the
		  dc driver at this time (see the BUGS section for details).
		  The original 82c168 appears on very early revisions of the
		  LinkSys LNE100TX and Matrox FastNIC.

     10baseT/UTP  Set 10Mbps operation.	 The mediaopt option can also be used
		  to enable full-duplex	operation.  Not	specifying full-duplex
		  implies half-duplex mode.

     100baseTX	  Set 100Mbps (Fast Ethernet) operation.  The mediaopt option
		  can also be used to enable full-duplex operation.  Not spec-
		  ifying full-duplex implies half-duplex mode.

     The dc driver supports the	following media	options:

     full-duplex  Force	full duplex operation.	The interface will operate in
		  half duplex mode if this media option	is not specified.

     Note that the 100baseTX media type	may not	be available on	certain	Intel
     21143 adapters which support 10Mbps media attachments only.  For more in-
     formation on configuring this device, see ifconfig(8).

     The dc driver provides support for	the following chipsets:

     o	 DEC/Intel 21143
     o	 ADMtek	AL981 Comet, AN985 Centaur, ADM9511 Centaur II and ADM9513
	 Centaur II
     o	 ALi/ULi M5261 and M5263
     o	 ASIX Electronics AX88140A and AX88141
     o	 Conexant LANfinity RS7112 (miniPCI)
     o	 Davicom DM9009, DM9100, DM9102	and DM9102A
     o	 Lite-On 82c168	and 82c169 PNIC
     o	 Lite-On/Macronix 82c115 PNIC II
     o	 Macronix 98713, 98713A, 98715,	98715A,	98715AEC-C, 98725, 98727 and
     o	 Xircom	X3201 (cardbus only)

     The following NICs	are known to work with the dc driver at	this time:

     o	 3Com OfficeConnect 10/100B (ADMtek AN985 Centaur-P)
     o	 Abocom	FE2500
     o	 Accton	EN1217 (98715A)
     o	 Accton	EN2242 MiniPCI
     o	 Adico AE310TX (98715A)
     o	 Alfa Inc GFC2204 (ASIX	AX88140A)
     o	 Built in 10Mbps only Ethernet on Compaq Presario 7900 series desktops
	 (21143, non-MII)
     o	 Built in Ethernet on LinkSys EtherFast	10/100 Instant GigaDrive
	 (DM9102, MII)
     o	 CNet Pro110B (ASIX AX88140A)
     o	 CNet Pro120A (98715A or 98713A) and CNet Pro120B (98715)
     o	 Compex	RL100-TX (98713	or 98713A)
     o	 D-Link	DFE-570TX (21143, MII, quad port)
     o	 Digital DE500-BA 10/100 (21143, non-MII)
     o	 ELECOM	Laneed LD-CBL/TXA (ADMtek AN985)
     o	 Hawking CB102 CardBus
     o	 IBM EtherJet Cardbus Adapter
     o	 Intel PRO/100 Mobile Cardbus (versions	that use the X3201 chipset)
     o	 Jaton XpressNet (Davicom DM9102)
     o	 Kingston KNE100TX (21143, MII)
     o	 Kingston KNE110TX (PNIC 82c169)
     o	 LinkSys LNE100TX (PNIC	82c168,	82c169)
     o	 LinkSys LNE100TX v2.0 (PNIC II	82c115)
     o	 LinkSys LNE100TX v4.0/4.1 (ADMtek AN985 Centaur-P)
     o	 Matrox	FastNIC	10/100 (PNIC 82c168, 82c169)
     o	 Melco LGY-PCI-TXL
     o	 Microsoft MN-120 10/100 CardBus (ADMTek Centaur-C)
     o	 Microsoft MN-130 10/100 PCI (ADMTek Centaur-P)
     o	 NDC SOHOware SFA110A (98713A)
     o	 NDC SOHOware SFA110A Rev B4 (98715AEC-C)
     o	 NetGear FA310-TX Rev. D1, D2 or D3 (PNIC 82c169)
     o	 Netgear FA511
     o	 PlaneX	FNW-3602-T (ADMtek AN985)
     o	 SMC EZ	Card 10/100 1233A-TX (ADMtek AN985)
     o	 SVEC PN102-TX (98713)
     o	 Xircom	Cardbus	Realport
     o	 Xircom	Cardbus	Ethernet 10/100
     o	 Xircom	Cardbus	Ethernet II 10/100

     dc%d: couldn't map	ports/memory  A	fatal initialization error has oc-

     dc%d: couldn't map	interrupt  A fatal initialization error	has occurred.

     dc%d: watchdog timeout  A packet was queued for transmission and a	trans-
     mit command was issued, but the device failed to acknowledge the trans-
     mission before a timeout expired.	This can happen	if the device is un-
     able to deliver interrupts	for some reason, of if there is	a problem with
     the network connection (cable or network equipment) that results in a
     loss of link.

     dc%d: no memory for rx list  The driver failed to allocate	an mbuf	for
     the receiver ring.

     dc%d: TX underrun -- increasing TX	threshold  The device generated	a
     transmit underrun error while attempting to DMA and transmit a packet.
     This happens if the host is not able to DMA the packet data into the
     NIC's FIFO	fast enough.  The driver will dynamically increase the trans-
     mit start threshold so that more data must	be DMAed into the FIFO before
     the NIC will start	transmitting it	onto the wire.

     dc%d: TX underrun -- using	store and forward mode	The device continued
     to	generate transmit underruns even after all possible transmit start
     threshold settings	had been tried,	so the driver programmed the chip for
     store and forward mode.  In this mode, the	NIC will not begin transmis-
     sion until	the entire packet has been transferred into its	FIFO memory.

     dc%d: chip	is in D3 power state --	setting	to D0  This message applies
     only to adapters which support power management.  Some operating systems
     place the controller in low power mode when shutting down,	and some PCI
     BIOSes fail to bring the chip out of this state before configuring	it.
     The controller loses all of its PCI configuration in the D3 state,	so if
     the BIOS does not set it back to full power mode in time, it will not be
     able to configure it correctly.  The driver tries to detect this condi-
     tion and bring the	adapter	back to	the D0 (full power) state, but this
     may not be	enough to return the driver to a fully operational condition.
     If	you see	this message at	boot time and the driver fails to attach the
     device as a network interface, you	will have to perform a second warm
     boot to have the device properly configured.

     Note that this condition only occurs when warm booting from another oper-
     ating system.  If you power down your system prior	to booting FreeBSD,
     the card should be	configured correctly.

     altq(4), arp(4), miibus(4), netintro(4), ng_ether(4), polling(4),
     vlan(4), ifconfig(8)

     ADMtek AL981, AL983 and AL985 data	sheets,

     ASIX Electronics AX88140A and AX88141 data	sheets,

     Davicom DM9102 data sheet,

     Intel 21143 Hardware Reference Manual,

     Macronix 98713/A, 98715/A and 98725 data sheets,

     Macronix 98713/A and 98715/A app notes,

     The dc device driver first	appeared in FreeBSD 4.0.

     The dc driver was written by Bill Paul <>.

     The Macronix application notes claim that in order	to put the chips in
     normal operation, the driver must write a certain magic number into the
     CSR16 register.  The numbers are documented in the	app notes, but the ex-
     act meaning of the	bits is	not.

     The 98713A	seems to have a	problem	with 10Mbps full duplex	mode.  The
     transmitter works but the receiver	tends to produce many unexplained er-
     rors leading to very poor overall performance.  The 98715A	does not ex-
     hibit this	problem.  All other modes on the 98713A	seem to	work cor-

     The original 82c168 PNIC chip has built in	NWAY support which is used on
     certain early LinkSys LNE100TX and	Matrox FastNIC cards, however it is
     horribly broken and difficult to use reliably.  Consequently, autonegoti-
     ation is not currently supported for this chipset:	the driver defaults
     the NIC to	10baseT	half duplex, and it is up to the operator to manually
     select a different	mode if	necessary.  (Later cards use an	external MII
     transceiver to implement NWAY autonegotiation and work correctly.)

     The dc driver programs 82c168 and 82c169 PNIC chips to use	the store and
     forward setting for the transmit start threshold by default.  This	is to
     work around problems with some NIC/PCI bus	combinations where the PNIC
     can transmit corrupt frames when operating	at 100Mbps, probably due to
     PCI DMA burst transfer errors.

     The 82c168	and 82c169 PNIC	chips also have	a receiver bug that sometimes
     manifests during periods of heavy receive and transmit activity, where
     the chip will improperly DMA received frames to the host.	The chips ap-
     pear to upload several kilobytes of garbage data along with the received
     frame data, dirtying several RX buffers instead of	just the expected one.
     The dc driver detects this	condition and will salvage the frame; however,
     it	incurs a serious performance penalty in	the process.

     The PNIC chips also sometimes generate a transmit underrun	error when the
     driver attempts to	download the receiver filter setup frame, which	can
     result in the receive filter being	incorrectly programmed.	 The dc	driver
     will watch	for this condition and requeue the setup frame until it	is
     transferred successfully.

     The ADMtek	AL981 chip (and	possibly the AN985 as well) has	been observed
     to	sometimes wedge	on transmit: this appears to happen when the driver
     queues a sequence of frames which cause it	to wrap	from the end of	the
     transmit descriptor ring back to the beginning.  The dc driver attempts
     to	avoid this condition by	not queuing any	frames past the	end of the
     transmit ring during a single invocation of the dc_start()	routine.  This
     workaround	has a negligible impact	on transmit performance.

FreeBSD	13.0		       December	26, 2020		  FreeBSD 13.0


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