Documentation/driver-api/ntb.rst

5 NTB (Non-Transparent Bridge) is a type of PCI-Express bridge chip that connects
6 the separate memory systems of two or more computers to the same PCI-Express
8 registers and memory translation windows, as well as non common features like
9 scratchpad and message registers. Scratchpad registers are read-and-writable
11 exchange a small amount of information at a fixed address. Message registers can
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42 inbound translation configured on the local ntb port and outbound translation
46  Inbound translation:
50  | dma-mapped |-ntb_mw_set_trans(addr)  |
52  | (addr)     |<======| MW xlat addr |<====| MW base addr |<== memory-mapped IO
53  |------------|       |--------------|  |  |--------------|
56 1) allocate a memory region, 2) put translated address to NTB config,
64  Outbound translation:
68  | dma-mapped |                |   | MW base addr |<== memory-mapped IO
69  | memory     |                |   |--------------|
70  | (addr)     |<===================| MW xlat addr |<-ntb_peer_mw_set_trans(addr)
71  |------------|                |   |--------------|
74 1) allocate a memory region, 2) somehow deliver a translated address to a peer
75 device, 3) peer puts the translated address to NTB config, 4) peer device maps
83   2) Initialize memory window by translated address of the allocated region
85   3) Send the translated address and memory window index to a peer device
88   1) Initialize memory window with retrieved address of the allocated
97   1) ntb_mw_count(pidx) - retrieve number of memory ranges, which can
100   2) ntb_get_align(pidx, midx) - retrieve parameters restricting the
105   4) ntb_mw_set_trans(pidx, midx) - try to set translation address of
107      (it may fail if local translated address setting is not supported)
108   5) Send translated base address (usually together with memory window
113   1) ntb_peer_mw_set_trans(pidx, midx) - try to set received from other
114      device (related to pidx) translated address for specified memory
115      window. It may fail if retrieved address, for instance, exceeds
116      maximum possible address or isn't properly aligned.
117   2) ntb_peer_mw_get_addr(widx) - retrieve MMIO address to map the memory
121 same value as ntb_peer_mw_count() on the peer with port index - pidx.
124 ------------------------------------------------------------------
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150 * unsafe - Some hardware has known issues with scratchpad and doorbell
154 * delay\_ms - Specify the delay between receiving a doorbell
157 * init\_db - Specify the doorbell bits to start new series of rounds.  A new
160 * dyndbg - It is suggested to specify dyndbg=+p when loading this module, and
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237 ------------------------------------------
248 	`-1`.
252 	second half of the memory window for address translation to the peer.
255 	this 64 bit address on the bus between the NTB devices for the window
257 * xeon\_b2b\_usd\_bar4\_addr64 - See *xeon\_b2b\_bar2\_addr64*.
258 * xeon\_b2b\_usd\_bar4\_addr32 - See *xeon\_b2b\_bar2\_addr64*.
259 * xeon\_b2b\_usd\_bar5\_addr32 - See *xeon\_b2b\_bar2\_addr64*.
260 * xeon\_b2b\_dsd\_bar2\_addr64 - See *xeon\_b2b\_bar2\_addr64*.
261 * xeon\_b2b\_dsd\_bar4\_addr64 - See *xeon\_b2b\_bar2\_addr64*.
262 * xeon\_b2b\_dsd\_bar4\_addr32 - See *xeon\_b2b\_bar2\_addr64*.
263 * xeon\_b2b\_dsd\_bar5\_addr32 - See *xeon\_b2b\_bar2\_addr64*.