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Nest (NX) Accelerator Coprocessor
---------------------------------
The NX coprocessor is present in P7+ or later processors. Each NX node
represents a unique NX coprocessor. The nodes are located under an
xscom node, as:
/xscom@<xscom_addr>/nx@<nx_addr>
With unique xscom and nx addresses. Their compatible node contains
"ibm,power-nx".
NX 842 Coprocessor
------------------
This is the memory compression coprocessor, which uses the IBM proprietary
842 compression algorithm and format. Each nx node contains an 842 engine.
ibm,842-coprocessor-type : CT value common to all 842 coprocessors
ibm,842-coprocessor-instance : CI value unique to all 842 coprocessors
Access to the coprocessor requires using the ICSWX instruction, which uses
a specific format including a Coprocessor Type (CT) and Coprocessor Instance
(CI) value to address each request to the right coprocessor. The driver should
use the CT and CI values for a particular node to communicate with it. For
all 842 coprocessors in the system, the CT value will (should) be the same,
while each will have a different CI value. The driver can use CI 0 to allow
the hardware to automatically select which coprocessor instance to use.
NX RNG Coprocessor
------------------
This is the Random Number Generator (RNG) coprocessor, which is a part
of each NX coprocessor. Each node represents a unique RNG coprocessor.
Its nodes are not under the main nx node, they are located at:
/hwrng@<addr> : RNG at address <addr>
ibm,chip-id : chip id where the RNG is
reg : address of the register to read from
Each read from the RNG register will provide a new random number.
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