133 lines
4.3 KiB
Groff
133 lines
4.3 KiB
Groff
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.\"
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.\" SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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.\"
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.\" Copyright (c) 2018 Panasas
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd March 2, 2018
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.Dt IMCSMB 4
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.Os
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.Sh NAME
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.Nm imcsmb
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.Nd Intel integrated Memory Controller (iMC) SMBus controller driver
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.Sh SYNOPSIS
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.Cd device pci
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.Cd device smbus
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.Cd device imcsmb
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.Pp
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Alternatively, to load the driver as a module at boot time, place the following
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line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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imcsmb_load="YES"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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driver provides
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.Xr smbus 4
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support for the SMBus controller functionality in the integrated Memory
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Controllers (iMCs) embedded in Intel Sandybridge-Xeon, Ivybridge-Xeon,
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Haswell-Xeon, and Broadwell-Xeon CPUs.
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Each CPU implements one or more iMCs, depending on the number of cores;
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each iMC implements two SMBus controllers (iMC-SMBs).
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The iMC-SMBs are used by the iMCs to read configuration information from the
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DIMMs during POST.
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They may also be used, by motherboard firmware or a BMC, to monitor the
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temperature of the DIMMs.
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.Pp
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The iMC-SMBs are
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.Sy not
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general-purpose SMBus controllers.
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By their nature, they are only ever attached to DIMMs, so they implement only
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the SMBus operations need for communicating with DIMMs.
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Specifically:
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.Pp
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.Bl -dash -offset indent -compact
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.It
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READB
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.It
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READW
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.It
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WRITEB
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.It
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WRITEW
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.El
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.Pp
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A more detailed discussion of the hardware and driver architecture can be found
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at the top of
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.Pa sys/dev/imcsmb/imcsmb_pci.c .
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.Sh WARNINGS
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As mentioned above, firmware might use the iMC-SMBs to read DIMM temperatures.
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The public iMC documentation does not describe any sort of coordination
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mechanism to prevent requests from different sources -- such as the motherboard
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firmware, a BMC, or the operating system -- from interfering with each other.
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.Pp
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.Bf Sy
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Therefore, it is highly recommended that developers contact the motherboard
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vendor for any board-specific instructions on how to disable and re-enable DIMM
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temperature monitoring.
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.Ef
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.Pp
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DIMM temperature monitoring should be disabled before returning from
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.Fn imcsmb_pci_request_bus ,
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and re-enabled before returning from
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.Fn imcsmb_pci_release_bus .
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The driver includes comments to that effect at the appropriate locations.
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The driver has been tested and shown to work, with only that type of
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modification, on certain motherboards from Intel.
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.Po
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Unfortunately, those modifications were based on material covered under a
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non-disclosure agreement, and therefore are not included in this driver.
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.Pc
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The driver has also been tested and shown to work as-is on various motherboards
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from SuperMicro.
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.Pp
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The
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.Xr smb 4
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driver will connect to the
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.Xr smbus 4
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instances created by
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.Nm .
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However, since the IMC-SMBs are not general-purpose SMBus controllers, using
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.Xr smbmsg 8
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with those
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.Xr smb 4
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devices is not supported.
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.Sh SEE ALSO
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.Xr jedec_dimm 4 ,
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.Xr smbus 4
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.Sh HISTORY
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The
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.Nm
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driver first appeared in
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.Fx 12.0 .
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.Sh AUTHORS
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The
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.Nm
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driver was originally written for Panasas by
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.An Joe Kloss .
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It was substantially refactored, and this manual page was written, by
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.An Ravi Pokala Aq Mt rpokala@freebsd.org
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