Copyright (c) 2014 Thomas Skibo <thomasskibo@yahoo.com>
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$FreeBSD: head/share/man/man4/man4.arm/cgem.4 271907 2014-09-20 15:45:29Z ian $
.Dd August 26, 2014 .Dt CGEM 4 .Os .Sh NAME .Nm cgem .Nd "Cadence GEM Gigabit Ethernet driver" .Sh SYNOPSIS To compile this driver into the kernel, place the following lines in your kernel configuration file: d -ragged -offset indent .Cd "device ether" .Cd "device miibus" .Cd "device cgem" .Ed .Sh DESCRIPTION The .Nm driver provides support for the Cadence GEM (Gigabit Ethernet MAC). The Cadence GEM is used in some SoC (System on a Chip) devices such as the Xilinx Zynq-7000 and the Atmel SAMA5D3.
p The .Nm driver supports the following media types: l -tag -width ".Cm 10baseT/UTP" t Cm autoselect Enable autoselection of the media type and options. The user can manually override the autoselected mode using .Xr ifconfig 8 or by adding media options to .Xr rc.conf 5 . t Cm 10baseT/UTP Set 10Mbps operation. The .Xr ifconfig 8 .Cm mediaopt option can also be used to select either .Cm full-duplex or .Cm half-duplex modes. t Cm 100baseTX Set 100Mbps (Fast Ethernet) operation. The .Xr ifconfig 8 .Cm mediaopt option can also be used to select either .Cm full-duplex or .Cm half-duplex modes. t Cm 1000baseT Set 1000Mbps (Gigabit Ethernet) operation over twisted pair. The GEM supports 1000Mbps in .Cm full-duplex mode only. .El
p The .Nm driver supports the following media options: l -tag -width ".Cm full-duplex" t Cm full-duplex Force full-duplex operation. t Cm half-duplex Force half-duplex operation. .El
p The driver provides support for TCP/UDP/IP checksum offloading (although disabled by default). The device and driver also support 1536-byte frames for VLANs (vlanmtu). .Sh SYSCTL VARIABLES The following variables are available as both .Xr sysctl 8 variables and .Xr loader 8 tunables: l -tag -width "xxxxxxxx" t Va dev.cgem.%d.rxbufs The number of receive buffers allocated to the hardware. The default value is 256. The maximum value is 511. If this number is increased while the interface is UP, it will not take effect until the next packet is received. If this number is decreased while the interface is UP, buffers will not be immediately removed from the receive buffer ring but the number of buffers will decrease as packets are received until it reaches the new value. t Va dev.cgem.%d.rxhangwar This tunable enables a work-around to recover from receive hangs. The default value is 1. Set to 0 to disable the work-around. .El
p The following read-only variables are available as .Xr sysctl 8 variables: l -tag -width "xxxxxxxx" t Va dev.cgem.%d._rxoverruns This variable counts the number of receive packet buffer overrun interrupts. t Va dev.cgem.%d._rxnobufs This variable counts the number of interrupts due to the GEM buffer ring going empty. t Va dev.cgem.%d._rxdmamapfails This variable is the number of times bus_dmamap_load_mbuf_sg(9) failed in the receive path. t Va dev.cgem.%d._txfull The number of times the GEM's transmit ring was full. t Va dev.cgem.%d._txdmamapfails This variable is the number of times bus_dmamap_load_mbuf_sg(9) failed in the transmit path. t Va dev.cgem.%d._txdefrags This variable is the number of times the driver needed to call m_defrag(9) because a packet queued for transmit had too many DMA segments. t Va dev.cgem.%d._txdefragfails This variable is the number of times .Xr m_defrag 9 failed. t Va dev.cgem.%d.stats.* The following variables are useful MAC counters supplied by the hardware: t Va dev.cgem.%d.stats.tx_bytes A 64-bit counter of the number of bytes transmitted in frames without error. t Va dev.cgem.%d.stats.tx_frames Counter of frames transmitted without error excluding pause frames. t Va dev.cgem.%d.stats.tx_frames_bcast Counter of broadcast frames transmitted without error excluding pause frames. t Va dev.cgem.%d.stats.tx_frames_multi Counter of multicast frames transmitted without error excluding pause frames. t Va dev.cgem.%d.stats.tx_frames_pause Counter of pause frames transmitted without error. t Va dev.cgem.%d.stats.tx_frames_64b Counter of 64 byte frames transmitted without error. t Va dev.cgem.%d.stats.tx_frames_65to127b Counter of 65 to 127 byte frames transmitted without error. t Va dev.cgem.%d.stats.tx_frames_128to255b Counter of 128 to 255 byte frames transmitted without error. t Va dev.cgem.%d.stats.tx_frames_256to511b Counter of 256 to 511 byte frames transmitted without error. t Va dev.cgem.%d.stats.tx_frames_512to1023b Counter of 512 to 1023 byte frames transmitted without error. t Va dev.cgem.%d.stats.tx_frames_1024to1536b Counter of 1024 to 1536 byte frames transmitted without error. t Va dev.cgem.%d.stats.tx_under_runs Counter of frames not transmitted due to a transmit underrun. t Va dev.cgem.%d.stats.tx_single_collisn Counter of frames experiencing a single collision before being successfully transmitted. t Va dev.cgem.%d.stats.tx_multi_collisn Counter of frames experiencing between 2 and 15 collisions before being successfully transmitted. t Va dev.cgem.%d.stats.tx_excsv_collisn Counter of frames that failed to transmit because they experienced 16 collisions. t Va dev.cgem.%d.stats.tx_late_collisn Counter of frames that experienced a late collision. t Va dev.cgem.%d.stats.tx_deferred_frames Counter of frames experiencing deferral due to carrier sense being active on their first attempt at transmission. t Va dev.cgem.%d.stats.tx_carrier_sense_errs Counter of frames transmitted where carrier sense was not seen during transmission or where carrier sense was deasserted after being asserted in a transmit frame without collision. t Va dev.cgem.%d.stats.rx_bytes A 64-bit counter of bytes received without error excluding pause frames. t Va dev.cgem.%d.stats.rx_frames Counter of frames received without error excluding pause frames. t Va dev.cgem.%d.stats.rx_frames_bcast Counter of broadcast frames receive without error excluding pause frames. t Va dev.cgem.%d.stats.rx_frames_multi Counter of multicast frames receive without error excluding pause frames. t Va dev.cgem.%d.stats.rx_frames_pause Counter of pause frames recevied without error. t Va dev.cgem.%d.stats.rx_frames_64b Counter of 64-byte frames received without error. t Va dev.cgem.%d.stats.rx_frames_65to127b Counter of 65 to 127 byte frames received without error. t Va dev.cgem.%d.stats.rx_frames_128to255b Counter of 128 to 255 byte frames received without error. t Va dev.cgem.%d.stats.rx_frames_256to511b Counter of 256 to 511 byte frames received without error. t Va dev.cgem.%d.stats.rx_frames_512to1023b Counter of 512 to 1023 byte frames received without error. t Va dev.cgem.%d.stats.rx_frames_1024to1536b Counter of 1024 to 1536 byte frames received without error. t Va dev.cgem.%d.stats.rx_frames_undersize Counter of frames received less than 64 bytes in length that do not also have either a CRC error or an alignment error. t Va dev.cgem.%d.stats.rx_frames_oversize Counter of frames received exceeding 1536 bytes and do not also have either a CRC error or an alignment error. t Va dev.cgem.%d.stats.rx_frames_jabber Counter of frames received exceeding 1536 bytes and also have either a CRC error, an alignment error, or a receive symbol error. t Va dev.cgem.%d.stats.rx_frames_fcs_errs Counter of frames received with a bad CRC and are between 64 and 1536 bytes. t Va dev.cgem.%d.stats.rx_frames_length_errs Counter of frames received that are shorter than that extracted from the length field. t Va dev.cgem.%d.stats.rx_symbol_errs Counter of receive symbol errors. t Va dev.cgem.%d.stats.rx_align_errs Counter of received frames that are not an integral number of bytes. t Va dev.cgem.%d.stats.rx_resource_errs Counter of frames successfully receive by the MAC but could not be copied to memory because no receive buffer was available. t Va dev.cgem.%d.stats.rx_overrun_errs Counter of frames that are address recognized but were not copied to memory due to a receive overrun. t Va dev.cgem.%d.stats.rx_frames_ip_hdr_csum_errs Counter of frames discarded due to an incorrect IP header checksum when checksum offloading is enabled. t Va dev.cgem.%d.stats.rx_frames_tcp_csum_errs Counter of frames discarded due to an incorrect TCP checksum when checksum offloading is enabled. t Va dev.cgem.%d.stats.rx_frames_udp_csum_errs Counter of frames discarded due to an incorrect UDP checksum when checksum offloading is enabled. .El .Sh BUGS The GEM can perform TCP/UDP/IP checksum offloading. However, when transmit checksum offloading is enabled, the GEM generates and replaces checksums for all packets it transmits. In a system that is forwarding packets, the device could potentially correct the checksum of packet that was corrupted in transit. For this reason, checksum offloading is disabled by default but can be enabled using ifconfig(8).
p When receive checksum offloading is enabled, the device will discard packets with bad TCP/UDP/IP checksums. The bad packets will not be counted in any .Xr netstat 1 statistics. There are .Xr sysctl 8 variables that count packets discarded by the hardware (see below).
p The GEM used in the Zynq-7000 has a bug such that the receiver can potentially freeze up under a high load. The issue is described in sec. 16.7 "Known Issues" of the Zynq-7000 SoC Technical Reference Manual (Xilinx UG585 v1.7). The .Nm driver implements the work-around suggested in the manual. If the bug does not exist in other versions of this device, the work-around can be disabled by setting the dev.cgem.%d.rxhangwar .Xr sysctl 8 variable to 0.
p .Sh SEE ALSO .Xr miibus 4 , .Xr ifconfig 8 .Rs .%T "Zynq-7000 SoC Technical Reference Manual (Xilinx doc UG585)" .%U http://www.xilinx.com/support/documentation/user_guides/\:ug585-Zynq-7000-TRM.pdf .Re .Sh HISTORY The .Nm device driver first appeared in .Fx 10.0 . .Sh AUTHORS The .Nm driver and this manual page was written by .An Thomas Skibo Aq Mt thomasskibo@yahoo.com .