Ubuntu Manpage: spu_run - execute an SPU context

NAME

       spu_run - execute an SPU context

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <sys/spu.h>          /* Definition of SPU_* constants */
       #include <sys/syscall.h>      /* Definition of SYS_* constants */
       #include <unistd.h>

       int syscall(SYS_spu_run, int fd, uint32_t *npc, uint32_t *event);

       Note: glibc provides no wrapper for spu_run(), necessitating the use of syscall(2).

DESCRIPTION

The spu_run() system call is used on PowerPC machines that implement the Cell Broadband
Engine Architecture in order to access Synergistic Processor Units (SPUs). The fd
argument is a file descriptor returned by spu_create(2) that refers to a specific SPU
context. When the context gets scheduled to a physical SPU, it starts execution at the
instruction pointer passed in npc.

Execution of SPU code happens synchronously, meaning that spu_run() blocks while the SPU
is still running. If there is a need to execute SPU code in parallel with other code on
either the main CPU or other SPUs, a new thread of execution must be created first (e.g.,
using pthread_create(3)).

When spu_run() returns, the current value of the SPU program counter is written to npc, so
successive calls to spu_run() can use the same npc pointer.

The event argument provides a buffer for an extended status code. If the SPU context was
created with the SPU_CREATE_EVENTS_ENABLED flag, then this buffer is populated by the
Linux kernel before spu_run() returns.

The status code may be one (or more) of the following constants:

SPE_EVENT_DMA_ALIGNMENT
A DMA alignment error occurred.

SPE_EVENT_INVALID_DMA
An invalid MFC DMA command was attempted.

SPE_EVENT_SPE_DATA_STORAGE
A DMA storage error occurred.

SPE_EVENT_SPE_ERROR
An illegal instruction was executed.

NULL is a valid value for the event argument. In this case, the events will not be
reported to the calling process.

RETURN VALUE

       On success, spu_run() returns the value  of  the  spu_status  register.   On  failure,  it
       returns -1 and sets errno is set to indicate the error.

       The  spu_status  register value is a bit mask of status codes and optionally a 14-bit code
       returned from the stop-and-signal instruction on the SPU.  The bit masks  for  the  status
       codes are:

       0x02   SPU was stopped by a stop-and-signal instruction.

       0x04   SPU was stopped by a halt instruction.

       0x08   SPU is waiting for a channel.

       0x10   SPU is in single-step mode.

       0x20   SPU has tried to execute an invalid instruction.

       0x40   SPU has tried to access an invalid channel.

       0x3fff0000
              The  bits  masked  with this value contain the code returned from a stop-and-signal
              instruction.  These bits are valid only if the 0x02 bit is set.

       If spu_run() has not returned an error, one or more bits among the lower  eight  ones  are
       always set.

ERRORS

       EBADF  fd is not a valid file descriptor.

       EFAULT npc is not a valid pointer, or event is non-NULL and an invalid pointer.

       EINTR  A  signal  occurred  while spu_run() was in progress; see signal(7).  The npc value
              has been updated to the new program counter value if necessary.

       EINVAL fd is not a valid file descriptor returned from spu_create(2).

       ENOMEM There was not enough memory available to handle  a  page  fault  resulting  from  a
              Memory Flow Controller (MFC) direct memory access.

       ENOSYS The  functionality  is  not  provided  by  the  current  system, because either the
              hardware does not provide SPUs or the spufs module is not loaded.

STANDARDS

       Linux on PowerPC.

HISTORY

       Linux 2.6.16.

NOTES

       spu_run() is meant to be used from libraries that implement a more abstract  interface  to
       SPUs,   not  to  be  used  from  regular  applications.   See  ⟨http://www.bsc.es/projects
       /deepcomputing/linuxoncell/⟩ for the recommended libraries.

EXAMPLES

       The following is an example of running a simple,  one-instruction  SPU  program  with  the
       spu_run() system call.

       #include <err.h>
       #include <fcntl.h>
       #include <stdint.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <sys/types.h>
       #include <unistd.h>

       int main(void)
       {
           int       context, fd, spu_status;
           uint32_t  instruction, npc;

           context = syscall(SYS_spu_create, "/spu/example-context", 0, 0755);
           if (context == -1)
               err(EXIT_FAILURE, "spu_create");

           /*
            * Write a 'stop 0x1234' instruction to the SPU's
            * local store memory.
            */
           instruction = 0x00001234;

           fd = open("/spu/example-context/mem", O_RDWR);
           if (fd == -1)
               err(EXIT_FAILURE, "open");
           write(fd, &instruction, sizeof(instruction));

           /*
            * set npc to the starting instruction address of the
            * SPU program. Since we wrote the instruction at the
            * start of the mem file, the entry point will be 0x0.
            */
           npc = 0;

           spu_status = syscall(SYS_spu_run, context, &npc, NULL);
           if (spu_status == -1)
               err(EXIT_FAILURE, "open");

           /*
            * We should see a status code of 0x12340002:
            *   0x00000002 (spu was stopped due to stop-and-signal)
            * | 0x12340000 (the stop-and-signal code)
            */
           printf("SPU Status: %#08x\n", spu_status);

           exit(EXIT_SUCCESS);
       }