2 .\" Copyright (c) 2019 Rajesh Kumar <rajesh1.kumar@amd.com>
3 .\" All rights reserved.
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31 .Nd AMD Non-Transparent Bridge driver
33 To compile this driver into your kernel,
34 place the following lines in your kernel configuration file:
35 .Bd -ragged -offset indent
37 .Cd "device ntb_hw_amd"
40 Or, to load the driver as a module at boot, place the following line in
42 .Bd -literal -offset indent
46 The following sysctls are supported in this driver
48 .It Va dev.ntb_hw.X.info
49 Reading this sysctl will give the basic details like the number of memory
50 windows, scratchpads and doorbells exposed by the NTB on the local host to
51 access the devices beyond the bridge.
52 It also provides details about the masked doorbells, translation address and
53 size limit of each exposed memory window and link status information.
58 driver provides support for the Non-Transparent Bridge (NTB) hardware in
59 AMD EPYC processor family.
60 The Non-Transparent Bridge does not look as a regular PCI bridge, but as PCI
61 endpoint device, hiding the devices behind it.
62 The driver hides details of hardware on the other side, but exposes memory windows,
63 scratchpads and doorbells to access the other side via hardware independent
68 The hardware provides 2 (both 64-bit) or 3 (one 32-bit and two 64-bit) memory
69 windows to the other system's memory, up to 16 scratchpad registers and 16
70 doorbells to communicate with and interrupt the other system respectively.
72 The NTB configuration should be set by BIOS.
73 This includes enabling NTB, choosing topology (only NTB-to-Root Port
74 mode is supported now), role of the host in the topology.
75 This needs to be done on both systems.
77 The BAR size for memory windows is configured to 1 MiB by default.
86 driver was developed by AMD and originally written by
87 .An Rajesh Kumar Aq Mt rajesh1.kumar@amd.com .
89 .An Alexander Motin Aq Mt mav@FreeBSD.org ,
90 .An Conrad E. Meyer Aq Mt cem@FreeBSD.org
92 .An Warner Losh Aq Mt imp@FreeBSD.org .