arch/powerpc/vas-api.rst

1 .. SPDX-License-Identifier: GPL-2.0
2 .. _VAS-API:
11 Power9 processor introduced Virtual Accelerator Switchboard (VAS) which
12 allows both userspace and kernel communicate to co-processor
14 unit comprises of one or more hardware engines or co-processor types
21 Requests to the GZIP engine must be formatted as a co-processor Request
38 /dev/crypto/nx-gzip device node implemented by the VAS/NX device driver.
39 An application must open the /dev/crypto/nx-gzip device to obtain a file
58 NX-GZIP Device Node
61 There is one /dev/crypto/nx-gzip node in the system and it provides
63 /dev/crypto/nx-gzip are:
68 	  address space (i.e. get a paste_address for the co-processor
78 Although a system may have several instances of the NX co-processor
80 /dev/crypto/nx-gzip device node in the system. When the nx-gzip device
86 Applications may chose a specific instance of the NX co-processor using
91 	 https://github.com/abalib/power-gzip
96 Open /dev/crypto/nx-gzip
99 The nx-gzip device should be opened for read and write. No special
111 a connection with NX co-processor engine:
117 			__s16   vas_id; /* specific instance of vas or -1
127 		If '-1' is passed, kernel will make a best-effort attempt
146 	returns -1 and sets the errno variable to indicate the error.
164 mmap() NX-GZIP device
167 The mmap() system call for a NX-GZIP device fd returns a paste_address
174 	Only restrictions on mmap for a NX-GZIP device fd are:
194 like /proc/device-tree/vas@* or /proc/device-tree/xscom@*/vas@*.
195 Determine the chip or VAS instance and use the corresponding ibm,vas-id
203 https://openpowerfoundation.org/?resource_lib=power-isa-version-3-0
208 Applications should format requests to the co-processor using the
209 co-processor Request Block (CRBs). Refer NX-GZIP user's manual for the format
217 co-processor Status Block (CSB) flags. NX updates status in CSB after each
218 request is processed. Refer NX-GZIP user's manual for the format of CSB and
245 In the case of multi-thread applications, NX send windows can be shared
256 NX-GZIP User's Manual:
257 https://github.com/libnxz/power-gzip/blob/master/doc/power_nx_gzip_um.pdf
270 			fd = open("/dev/crypto/nx-gzip", O_RDWR);
272 				fprintf(stderr, "open nx-gzip failed\n");
273 				return -1;
277 			txattr.vas_id = -1
290 				return -errno;
304 	Refer https://github.com/libnxz/power-gzip for tests or more