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