NTB_HW_AMD(4)          FreeBSD Kernel Interfaces Manual          NTB_HW_AMD(4)

NAME
     ntb_hw_amd - AMD Non-Transparent Bridge driver

SYNOPSIS
     To compile this driver into your kernel, place the following lines in
     your kernel configuration file:

           device ntb
           device ntb_hw_amd

     Or, to load the driver as a module at boot, place the following line in
     loader.conf(5):

           ntb_hw_amd_load="YES"

     The following sysctls are supported in this driver

     dev.ntb_hw.X.info
     Reading this sysctl will give the basic details like the number of memory
     windows, scratchpads and doorbells exposed by the NTB on the local host
     to access the devices beyond the bridge.  It also provides details about
     the masked doorbells, translation address and size limit of each exposed
     memory window and link status information.

DESCRIPTION
     The ntb_hw_amd driver provides support for the Non-Transparent Bridge
     (NTB) hardware in AMD EPYC processor family.  The Non-Transparent Bridge
     does not look as a regular PCI bridge, but as PCI endpoint device, hiding
     the devices behind it.  The driver hides details of hardware on the other
     side, but exposes memory windows, scratchpads and doorbells to access the
     other side via hardware independent KPI to ntb(4) subsystem.

     The hardware provides 2 (both 64-bit) or 3 (one 32-bit and two 64-bit)
     memory windows to the other system's memory, up to 16 scratchpad
     registers and 16 doorbells to communicate with and interrupt the other
     system respectively.

CONFIGURATION
     The NTB configuration should be set by BIOS.  This includes enabling NTB,
     choosing topology (only NTB-to-Root Port mode is supported now), role of
     the host in the topology.  This needs to be done on both systems.

     The BAR size for memory windows is configured to 1 MiB by default.

SEE ALSO
     if_ntb(4), ntb(4), ntb_transport(4)

AUTHORS
     The ntb_hw_amd driver was developed by AMD and originally written by
     Rajesh Kumar <rajesh1.kumar@amd.com>.  Reviewed by Alexander Motin
     <mav@FreeBSD.org>, Conrad E. Meyer <cem@FreeBSD.org> and Warner Losh
     <imp@FreeBSD.org>.

FreeBSD 13.1-RELEASE-p6         August 29, 2019        FreeBSD 13.1-RELEASE-p6