1.\" $NetBSD: imcsmb.4,v 1.10 2020/11/14 20:04:46 wiz Exp $ 2.\" 3.\" Copyright (c) 2018 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Paul Goyette 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.\" SPDX-License-Identifier: BSD-2-Clause-FreeBSD 31.\" 32.\" Copyright (c) 2018 Panasas 33.\" All rights reserved. 34.\" 35.\" Redistribution and use in source and binary forms, with or without 36.\" modification, are permitted provided that the following conditions 37.\" are met: 38.\" 1. Redistributions of source code must retain the above copyright 39.\" notice, this list of conditions and the following disclaimer. 40.\" 2. Redistributions in binary form must reproduce the above copyright 41.\" notice, this list of conditions and the following disclaimer in the 42.\" documentation and/or other materials provided with the distribution. 43.\" 44.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 45.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 46.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 47.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 48.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 49.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 50.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 51.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 52.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 53.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 54.\" 55.\" $FreeBSD$ 56.\" 57.Dd April 16, 2020 58.Dt IMCSMB 4 x86 59.Os 60.Sh NAME 61.Nm imcsmb 62.Nd Intel integrated Memory Controller (iMC) SMBus controller driver 63.Sh SYNOPSIS 64.Cd "imc* at pci? dev ? func ?" 65.Cd "imcsmb* at imc?" 66.Cd "iic* at i2cbus?" 67.Pp 68Alternatively, to load the driver as a module at boot time, place the following 69line in 70.Xr boot.cfg 5 : 71.Pp 72.Dl load=imcsmb 73.Pp 74or add the following line to your /etc/modules file: 75.Pp 76.Dl imcsmb 77.Sh DESCRIPTION 78The 79.Nm 80driver provides 81.Xr iic 4 82support for the SMBus controller functionality in the integrated Memory 83Controllers (iMCs) embedded in Intel Sandybridge-Xeon, Ivybridge-Xeon, 84Haswell-Xeon, and Broadwell-Xeon CPUs. 85Each CPU implements one or more iMCs, depending on the number of cores; each 86iMC implements two SMBus controllers (iMC-SMBs). 87The iMC-SMBs are used by the iMCs to read configuration information from the 88DIMMs during POST. 89They may also be used, by motherboard firmware or a BMC, to monitor the 90temperature of the DIMMs. 91.Pp 92The iMC-SMBs are 93.Sy not 94general-purpose SMBus controllers. 95By their nature, they are only ever attached to DIMMs, so they implement only 96the SMBus operations needed for communicating with DIMMs. 97Specifically: 98.Pp 99.Bl -dash -offset indent -compact 100.It 101READB 102.It 103READW 104.It 105WRITEB 106.It 107WRITEW 108.El 109.Pp 110A more detailed discussion of the hardware and driver architecture can be found 111at the top of 112.Pa sys/dev/imcsmb/imc.c . 113.Sh WARNINGS 114As mentioned above, firmware might use the iMC-SMBs to read DIMM temperatures. 115The public iMC documentation does not describe any sort of coordination 116mechanism to prevent requests from different sources \(em such as the motherboard 117firmware, a BMC, or the operating system \(em from interfering with each other. 118.Pp 119.Bf Sy 120Therefore, it is highly recommended that developers contact the motherboard 121vendor for any board-specific instructions on how to disable and re-enable DIMM 122temperature monitoring. 123.Ef 124.Pp 125DIMM temperature monitoring should be disabled before returning from 126.Fn imcsmb_pci_request_bus , 127and re-enabled before returning from 128.Fn imcsmb_pci_release_bus . 129The driver includes comments to that effect at the appropriate locations. 130The driver has been tested and shown to work, with only that type of 131modification, on certain motherboards from Intel. 132(Unfortunately, those modifications were based on material covered under a 133non-disclosure agreement, and therefore are not included in this driver.) 134The driver has also been tested and shown to work as-is on various motherboards 135from SuperMicro and ASUS. 136.Pp 137Because of the above, the 138.Nm 139driver is not included in the default 140.Dv GENERIC 141kernel. 142In order to use the 143.Nm 144driver, you must compile a custom kernel, or load the driver using 145.Xr modload 8 . 146.Pp 147The 148.Xr iic 4 149driver will connect to the i2cbus instances created by 150.Nm . 151.Sh SEE ALSO 152.Xr iic 4 153.Sh HISTORY 154The 155.Nm 156driver first appeared in 157.Fx 12.0 . 158It was later ported to 159.Nx 9.0 . 160.Sh AUTHORS 161.An -nosplit 162The 163.Nm 164driver was originally written for Panasas by 165.An Joe Kloss . 166It was substantially refactored, and this manual page was written, by 167.An Ravi Pokala Aq Mt rpokala@freebsd.org . 168It was adapted to 169.Nx 170by 171.An Paul Goyette Aq Mt pgoyette@NetBSD.org . 172