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DC(4) DragonFly Kernel Interfaces Manual DC(4)
dc - DEC/Intel 21143 and clone 10/100 ethernet driver
The dc driver provides support for several PCI fast ethernet adapters and
embedded controllers based on the following chipsets:
* DEC/Intel 21143
* Macronix 98713, 98713A, 98715, 98715A and 98725
* Davicom DM9100, DM9102 and DM9102A
* ASIX Electronics AX88140A and AX88141
* ADMtek AL981 Comet and AN985 Centaur
* Lite-On 82c168 and 82c169 PNIC
* Lite-On/Macronix 82c115 PNIC II
* Conexant LANfinity RS7112 (miniPCI)
* Abocom FE2500
All of these chips have the same general register layout, DMA descriptor
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 programming options
including perfect filtering, inverse perfect filtering and hash table
Some clone chips duplicate the 21143 fairly closely while others only
maintain superficial similarities. Some support only MII media
attachments. 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 order 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 following NICs are known to
work with the dc driver at this time:
* Digital DE500-BA 10/100 (21143, non-MII)
* Built in 10Mbps only ethernet on Compaq Presario 7900 series
desktops (21143, non-MII)
* Built in ethernet on LinkSys EtherFast 10/100 Instant GigaDrive
* Kingston KNE100TX (21143, MII)
* D-Link DFE-570TX (21143, MII, quad port)
* NDC SOHOware SFA110 (98713A)
* SVEC PN102-TX (98713)
* CNet Pro120A (98715A or 98713A) and CNet Pro120B (98715)
* Compex RL100-TX (98713 or 98713A)
* LinkSys LNE100TX (PNIC 82c168, 82c169)
* NetGear FA310-TX Rev. D1, D2 or D3 (PNIC 82c169)
* Matrox FastNIC 10/100 (PNIC 82c168, 82c169)
* Kingston KNE110TX (PNIC 82c169)
* LinkSys LNE100TX v2.0 (PNIC II 82c115)
* Jaton XpressNet (Davicom DM9102)
* Alfa Inc GFC2204 (ASIX AX88140A)
* CNet Pro110B (ASIX AX88140A)
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
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 specifying 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
Note that the 100baseTX media type may not be available on certain Intel
21143 adapters which support 10mbps media attachments only.
For more information on configuring this device, see ifconfig(8). The dc
driver supports polling(4).
dc%d: couldn't map ports/memory A fatal initialization error has
dc%d: couldn't map interrupt A fatal initialization error has occurred.
dc%d: watchdog timeout A packet was queued for transmission and a
transmit command was issued, but the device failed to acknowledge the
transmission before a timeout expired. This can happen if the device is
unable 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
transmit 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
transmission until the entire packet has been transferred into its FIFO
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 won't be
able to configure it correctly. The driver tries to detect this
condition 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
operating system. If you power down your system prior to booting
DragonFly, the card should be configured correctly.
arp(4), ifmedia(4), miibus(4), netintro(4), ng_ether(4), polling(4),
ADMtek AL981, AL983 and AL985 data sheets, http://www.admtek.com.tw.
ASIX Electronics AX88140A and AX88141 data sheets,
Davicom DM9102 data sheet, http://www.davicom.com.tw.
Intel 21143 Hardware Reference Manual, http://developer.intel.com.
Macronix 98713/A, 98715/A and 98725 data sheets, http://www.macronix.com.
Macronix 98713/A and 98715/A app notes, http://www.macronix.com.
The dc device driver first appeared in FreeBSD 4.0.
The dc driver was written by Bill Paul <firstname.lastname@example.org>.
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
exact 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
errors leading to very poor overall performance. The 98715A does not
exhibit this problem. All other modes on the 98713A seem to work
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,
autonegotiation is not currently supported for this chipset: the driver
defaults the NIC to 10baseT half duplex, and it's 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
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
appear 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
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 queueing 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.
DragonFly 5.9-DEVELOPMENT November 14, 2010 DragonFly 5.9-DEVELOPMENT