1.\" 2.\" Copyright (c) 2014 Thomas Skibo <thomasskibo@yahoo.com> 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. The name of the author may not be used to endorse or promote products 11.\" derived from this software without specific prior written permission. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd January 10, 2021 28.Dt CGEM 4 29.Os 30.Sh NAME 31.Nm cgem 32.Nd "Cadence GEM Gigabit Ethernet driver" 33.Sh SYNOPSIS 34To compile this driver into the kernel, 35place the following lines in your 36kernel configuration file: 37.Bd -ragged -offset indent 38.Cd "device ether" 39.Cd "device miibus" 40.Cd "device cgem" 41.Ed 42.Sh DESCRIPTION 43The 44.Nm 45driver provides support for the Cadence GEM (Gigabit Ethernet MAC). 46The Cadence GEM is used in some SoC (System on a Chip) devices such as 47the Xilinx Zynq-7000, the Xilinx Zynq UltraScale+, and the SiFive 48HiFive Unleashed. 49.Pp 50The 51.Nm 52driver supports the following media types: 53.Bl -tag -width ".Cm 10baseT/UTP" 54.It Cm autoselect 55Enable autoselection of the media type and options. 56The user can manually override 57the autoselected mode using 58.Xr ifconfig 8 59or by adding media options to 60.Xr rc.conf 5 . 61.It Cm 10baseT/UTP 62Set 10Mbps operation. 63The 64.Xr ifconfig 8 65.Cm mediaopt 66option can also be used to select either 67.Cm full-duplex 68or 69.Cm half-duplex 70modes. 71.It Cm 100baseTX 72Set 100Mbps (Fast Ethernet) operation. 73The 74.Xr ifconfig 8 75.Cm mediaopt 76option can also be used to select either 77.Cm full-duplex 78or 79.Cm half-duplex 80modes. 81.It Cm 1000baseT 82Set 1000Mbps (Gigabit Ethernet) operation over twisted pair. 83The GEM supports 1000Mbps in 84.Cm full-duplex 85mode only. 86.El 87.Pp 88The 89.Nm 90driver supports the following media options: 91.Bl -tag -width ".Cm full-duplex" 92.It Cm full-duplex 93Force full-duplex operation. 94.It Cm half-duplex 95Force half-duplex operation. 96.El 97.Pp 98The driver provides support for TCP/UDP/IP checksum offloading (although 99disabled by default). 100The device and driver also support 1536-byte frames for VLANs (vlanmtu). 101.Sh SYSCTL VARIABLES 102The following variables are available as both 103.Xr sysctl 8 104variables and 105.Xr loader 8 106tunables: 107.Bl -tag -width "xxxxxxxx" 108.It Va dev.cgem.%d.rxbufs 109The number of receive buffers allocated to the hardware. 110The default value is 256. 111The maximum value is 511. 112If this number is increased while the interface is UP, it will not 113take effect until the next packet is received. 114If this number is decreased while the interface is UP, buffers will 115not be immediately removed from the receive buffer ring but the 116number of buffers will decrease as packets are received until it 117reaches the new value. 118.It Va dev.cgem.%d.rxhangwar 119This tunable enables a work-around to recover from receive hangs. 120The default value is 1. 121Set to 0 to disable the work-around. 122.El 123.Pp 124The following read-only variables are available as 125.Xr sysctl 8 126variables: 127.Bl -tag -width "xxxxxxxx" 128.It Va dev.cgem.%d._rxoverruns 129This variable counts the number of receive packet buffer overrun interrupts. 130.It Va dev.cgem.%d._rxnobufs 131This variable counts the number of interrupts due to the GEM buffer ring 132going empty. 133.It Va dev.cgem.%d._rxdmamapfails 134This variable is the number of times bus_dmamap_load_mbuf_sg(9) failed in 135the receive path. 136.It Va dev.cgem.%d._txfull 137The number of times the GEM's transmit ring was full. 138.It Va dev.cgem.%d._txdmamapfails 139This variable is the number of times bus_dmamap_load_mbuf_sg(9) failed in 140the transmit path. 141.It Va dev.cgem.%d._txdefrags 142This variable is the number of times the driver needed to call m_defrag(9) 143because a packet queued for transmit had too many DMA segments. 144.It Va dev.cgem.%d._txdefragfails 145This variable is the number of times 146.Xr m_defrag 9 147failed. 148.It Va dev.cgem.%d.stats.* 149The following variables are useful MAC counters supplied by the hardware: 150.It Va dev.cgem.%d.stats.tx_bytes 151A 64-bit counter of the number of bytes transmitted in frames without error. 152.It Va dev.cgem.%d.stats.tx_frames 153Counter of frames transmitted without error excluding pause frames. 154.It Va dev.cgem.%d.stats.tx_frames_bcast 155Counter of broadcast frames transmitted without error excluding 156pause frames. 157.It Va dev.cgem.%d.stats.tx_frames_multi 158Counter of multicast frames transmitted without error excluding 159pause frames. 160.It Va dev.cgem.%d.stats.tx_frames_pause 161Counter of pause frames transmitted without error. 162.It Va dev.cgem.%d.stats.tx_frames_64b 163Counter of 64 byte frames transmitted without error. 164.It Va dev.cgem.%d.stats.tx_frames_65to127b 165Counter of 65 to 127 byte frames transmitted without error. 166.It Va dev.cgem.%d.stats.tx_frames_128to255b 167Counter of 128 to 255 byte frames transmitted without error. 168.It Va dev.cgem.%d.stats.tx_frames_256to511b 169Counter of 256 to 511 byte frames transmitted without error. 170.It Va dev.cgem.%d.stats.tx_frames_512to1023b 171Counter of 512 to 1023 byte frames transmitted without error. 172.It Va dev.cgem.%d.stats.tx_frames_1024to1536b 173Counter of 1024 to 1536 byte frames transmitted without error. 174.It Va dev.cgem.%d.stats.tx_under_runs 175Counter of frames not transmitted due to a transmit underrun. 176.It Va dev.cgem.%d.stats.tx_single_collisn 177Counter of frames experiencing a single collision before being successfully 178transmitted. 179.It Va dev.cgem.%d.stats.tx_multi_collisn 180Counter of frames experiencing between 2 and 15 collisions before 181being successfully transmitted. 182.It Va dev.cgem.%d.stats.tx_excsv_collisn 183Counter of frames that failed to transmit because they experienced 16 184collisions. 185.It Va dev.cgem.%d.stats.tx_late_collisn 186Counter of frames that experienced a late collision. 187.It Va dev.cgem.%d.stats.tx_deferred_frames 188Counter of frames experiencing deferral due to carrier sense being 189active on their first attempt at transmission. 190.It Va dev.cgem.%d.stats.tx_carrier_sense_errs 191Counter of frames transmitted where carrier sense was not seen during 192transmission or where carrier sense was deasserted after being asserted 193in a transmit frame without collision. 194.It Va dev.cgem.%d.stats.rx_bytes 195A 64-bit counter of bytes received without error excluding pause 196frames. 197.It Va dev.cgem.%d.stats.rx_frames 198Counter of frames received without error excluding pause frames. 199.It Va dev.cgem.%d.stats.rx_frames_bcast 200Counter of broadcast frames receive without error excluding pause frames. 201.It Va dev.cgem.%d.stats.rx_frames_multi 202Counter of multicast frames receive without error excluding pause frames. 203.It Va dev.cgem.%d.stats.rx_frames_pause 204Counter of pause frames recevied without error. 205.It Va dev.cgem.%d.stats.rx_frames_64b 206Counter of 64-byte frames received without error. 207.It Va dev.cgem.%d.stats.rx_frames_65to127b 208Counter of 65 to 127 byte frames received without error. 209.It Va dev.cgem.%d.stats.rx_frames_128to255b 210Counter of 128 to 255 byte frames received without error. 211.It Va dev.cgem.%d.stats.rx_frames_256to511b 212Counter of 256 to 511 byte frames received without error. 213.It Va dev.cgem.%d.stats.rx_frames_512to1023b 214Counter of 512 to 1023 byte frames received without error. 215.It Va dev.cgem.%d.stats.rx_frames_1024to1536b 216Counter of 1024 to 1536 byte frames received without error. 217.It Va dev.cgem.%d.stats.rx_frames_undersize 218Counter of frames received less than 64 bytes in length that 219do not also have either a CRC error or an alignment error. 220.It Va dev.cgem.%d.stats.rx_frames_oversize 221Counter of frames received exceeding 1536 bytes and do not also have either 222a CRC error or an alignment error. 223.It Va dev.cgem.%d.stats.rx_frames_jabber 224Counter of frames received exceeding 1536 bytes and also have either a CRC 225error, an alignment error, or a receive symbol error. 226.It Va dev.cgem.%d.stats.rx_frames_fcs_errs 227Counter of frames received with a bad CRC and are between 64 228and 1536 bytes. 229.It Va dev.cgem.%d.stats.rx_frames_length_errs 230Counter of frames received that are shorter than that extracted 231from the length field. 232.It Va dev.cgem.%d.stats.rx_symbol_errs 233Counter of receive symbol errors. 234.It Va dev.cgem.%d.stats.rx_align_errs 235Counter of received frames that are not an integral number of bytes. 236.It Va dev.cgem.%d.stats.rx_resource_errs 237Counter of frames successfully receive by the MAC but could not be 238copied to memory because no receive buffer was available. 239.It Va dev.cgem.%d.stats.rx_overrun_errs 240Counter of frames that are address recognized but were not copied 241to memory due to a receive overrun. 242.It Va dev.cgem.%d.stats.rx_frames_ip_hdr_csum_errs 243Counter of frames discarded due to an incorrect IP header checksum when 244checksum offloading is enabled. 245.It Va dev.cgem.%d.stats.rx_frames_tcp_csum_errs 246Counter of frames discarded due to an incorrect TCP checksum when 247checksum offloading is enabled. 248.It Va dev.cgem.%d.stats.rx_frames_udp_csum_errs 249Counter of frames discarded due to an incorrect UDP checksum when 250checksum offloading is enabled. 251.El 252.Sh SEE ALSO 253.Xr miibus 4 , 254.Xr ifconfig 8 255.Rs 256.%T "Zynq-7000 SoC Technical Reference Manual (Xilinx doc UG585)" 257.%U http://www.xilinx.com/support/documentation/user_guides/\:ug585-Zynq-7000-TRM.pdf 258.Re 259.Sh HISTORY 260The 261.Nm 262device driver first appeared in 263.Fx 10.0 . 264.Sh AUTHORS 265The 266.Nm 267driver and this manual page was written by 268.An Thomas Skibo Aq Mt thomasskibo@yahoo.com . 269.Sh BUGS 270The GEM can perform TCP/UDP/IP checksum offloading. 271However, when transmit checksum offloading is enabled, the GEM generates and 272replaces checksums for all packets it transmits. 273In a system that is forwarding packets, the device could potentially correct 274the checksum of packet that was corrupted in transit. 275For this reason, checksum offloading is disabled by default but can be 276enabled using ifconfig(8). 277.Pp 278When receive checksum offloading is enabled, the device will discard packets 279with bad TCP/UDP/IP checksums. 280The bad packets will not be counted in any 281.Xr netstat 1 282statistics. 283There are 284.Xr sysctl 8 285variables that count 286packets discarded by the hardware (see below). 287.Pp 288The GEM used in the Zynq-7000 has a bug such that the receiver can 289potentially freeze up under a high load. 290The issue is described in sec. 16.7 291"Known Issues" of the Zynq-7000 SoC Technical Reference Manual (Xilinx 292UG585 v1.7). 293The 294.Nm 295driver implements the work-around suggested in the manual. 296It is believed that the bug does not exist in the Zynq UltraScale+ and 297SiFive SoCs so the work-around is disabled in those instances and enabled 298in all others. 299The work-around can be disabled by setting the 300.Va dev.cgem.%d.rxhangwar 301.Xr sysctl 8 302variable to 0. 303