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JME(4)                DragonFly Kernel Interfaces Manual                JME(4)


NAME

     jme -- JMicron Gigabit/Fast Ethernet driver


SYNOPSIS

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

           device miibus
           device jme

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

           if_jme_load="YES"


DESCRIPTION

     The jme device driver provides support for JMicron JMC250 PCI Express
     Gigabit Ethernet controllers and JMicron JMC260 PCI Express Fast Ethernet
     controllers.

     All LOMs supported by the jme driver have TCP/UDP/IP checksum offload for
     both transmit and receive, TCP segmentation offload (TSO), receive side
     scaling (RSS), multiple vector MSI-X, hardware VLAN tag
     stripping/insertion features, an interrupt coalescing/moderation
     mechanism as well as a 64-bit multicast hash filter.  Up to 4 reception
     queues can be enabled.  By default, the jme driver will try enabling as
     many reception queues as allowed by the number of CPUs in the system.

     The JMC250 also supports Jumbo Frames (up to 9216 bytes), which can be
     configured via the interface MTU setting.  Selecting an MTU larger than
     1500 bytes with the ifconfig(8) utility configures the adapter to receive
     and transmit Jumbo Frames.

     The jme 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 rc.conf(5).

     10baseT/UTP  Set 10Mbps operation.

     100baseTX    Set 100Mbps (Fast Ethernet) operation.

     1000baseT    Set 1000baseT operation over twisted pair.

     The jme driver supports the following media options:

     full-duplex  Force full duplex operation.

     half-duplex  Force half duplex operation.

     For more information on configuring this device, see ifconfig(8).  The
     jme driver supports polling(4).

   Loader Tunables
     By default, the driver will use MSI-X if it is supported.  This behavior
     can be turned off by setting the following tunable: (X is the device unit
     number):

           hw.jme.msix.enable=0
           hw.jmeX.msix.enable=0

     If MSI-X is disabled, the driver will use MSI if it is supported.  This
     behavior can be turned off by setting the following tunable:

           hw.jme.msi.enable=0
           hw.jmeX.msi.enable=0

     If MSI is used, MSI's target CPU can be changed by the following tunable:

           hw.jmeX.msi.cpu

     The maximum allowed value for this tunable is the number of CPUs minus
     one.

     Number of reception queues that can be enabled:

           hw.jme.rx_ring_count
           hw.jmeX.rx_ring_count

     Maximum allowed value for these tunables is 4.  Setting these tunables to
     0 allows driver to enable as many reception queues as allowed by the
     number of CPUs.

     Number of reception descriptors that can be used:

           hw.jme.rx_desc_count
           hw.jmeX.rx_desc_count

     Maximum allowed value for these tunables is 1024.

     Number of transmission descriptors that can be used:

           hw.jme.tx_desc_count
           hw.jmeX.tx_desc_count

     Maximum allowed value for these tunables is 1024.

   MIB Variables
     A number of per-interface variables are implemented in the dev.jme.X
     branch of the sysctl(3) MIB.

     tx_coal_to     Maximum amount of time to delay for TX completion
                    interrupt in units of 1us.  The accepted range is 1 to
                    65535, the default is 250 (250us).

     tx_coal_pkt    Maximum number of packets to fire TX completion interrupt.
                    The accepted range is 0 to 255, the default is 128.
                    Packet count based TX interrupt coalescing could be
                    disabled by setting this variable to 0.

     rx_coal_to     Maximum amount of time to delay for RX completion
                    interrupt in units of 1us.  The accepted range is 1 to
                    65535, the default is 150 (150us).

     rx_coal_pkt    Maximum number of packets to fire RX completion interrupt.
                    The accepted range is 0 to 255, the default is 64.  Packet
                    count based RX interrupt coalescing could be disabled by
                    setting this variable to 0.

     rx_desc_count  Number of RX descriptors per-ring (read-only).  Use the
                    tunable hw.jme.rx_desc_count to configure it.

     tx_desc_count  Number of TX descriptors (read-only).  Use the tunable
                    hw.jme.tx_desc_count to configure it.

     rx_ring_count  Number of RX rings (read-only).  Use the tunable
                    hw.jme.rx_ring_count to configure it.

     tx_wreg        The number of transmission descriptors should be setup
                    before the hardware register is written.  Setting this
                    value too high will have negative effect on transmission
                    timeliness.  Setting this value too low will hurt overall
                    transmission due to the frequent hardware register
                    writing.


SEE ALSO

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


HISTORY

     The jme driver was written by Pyun YongHyeon <yongari@FreeBSD.org>.  It
     first appeared in FreeBSD 7.1 and was imported into DragonFly 2.1.
     Sepherosa Ziehau added the receive side scaling and multiple vector MSI-X
     support to DragonFly.

DragonFly 4.7                    May 29, 2017                    DragonFly 4.7

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