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);
       }