| IMCSMB(4) | Device Drivers Manual | IMCSMB(4) |
imcsmb — Intel
integrated Memory Controller (iMC) SMBus controller driver
device pci
device smbus
device imcsmb
Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):
imcsmb_load="YES"
The imcsmb driver provides
smbus(4) support for the SMBus controller functionality in
the integrated Memory Controllers (iMCs) embedded in Intel Sandybridge-Xeon,
Ivybridge-Xeon, Haswell-Xeon, and Broadwell-Xeon CPUs. Each CPU implements
one or more iMCs, depending on the number of cores; each iMC implements two
SMBus controllers (iMC-SMBs). The iMC-SMBs are used by the iMCs to read
configuration information from the DIMMs during POST. They may also be used,
by motherboard firmware or a BMC, to monitor the temperature of the
DIMMs.
The iMC-SMBs are not general-purpose SMBus controllers. By their nature, they are only ever attached to DIMMs, so they implement only the SMBus operations need for communicating with DIMMs. Specifically:
A more detailed discussion of the hardware and driver architecture can be found at the top of sys/dev/imcsmb/imcsmb_pci.c.
As mentioned above, firmware might use the iMC-SMBs to read DIMM temperatures. The public iMC documentation does not describe any sort of coordination mechanism to prevent requests from different sources -- such as the motherboard firmware, a BMC, or the operating system -- from interfering with each other.
DIMM temperature monitoring should be
disabled before returning from
imcsmb_pci_request_bus(),
and re-enabled before returning from
imcsmb_pci_release_bus().
The driver includes comments to that effect at the appropriate locations.
The driver has been tested and shown to work, with only that type of
modification, on certain motherboards from Intel. (Unfortunately, those
modifications were based on material covered under a non-disclosure
agreement, and therefore are not included in this driver.) The driver has
also been tested and shown to work as-is on various motherboards from
SuperMicro.
The smb(4) driver will connect to the
smbus(4) instances created by
imcsmb. However, since the IMC-SMBs are not
general-purpose SMBus controllers, using smbmsg(8) with
those smb(4) devices is not supported.
The imcsmb driver first appeared in
FreeBSD 12.0.
The imcsmb driver was originally written
for Panasas by Joe Kloss. It was substantially
refactored, and this manual page was written, by
Ravi Pokala
<rpokala@freebsd.org>
| March 2, 2018 | Debian |