src/ppu/internal/dma/imoc_dma-tags_ppu.c

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#include <stdint.h>

#include <moc.h>
#include <internal/ppu/imoc_core_ppu.h>
#include <internal/ppu/imoc_dma_ppu.h>

/*
 * Methods for PPE tag reservation system needed for IGet and IPut. Per SPE the PPE can reserve Tags 0-14. Tag 15 is used by
 * blocking Get and Put, and more tags are not allowed on the PPE
 */

static unsigned short tags[8];

int moc_tag_reserve(unsigned int speid)
    {
    if (speid > 8)
        return MOC_ERR_INTERN;
    int i;
    unsigned short bit_tag = 1;
    for (i = 0; i < 15; i++)
        {
        // if last position is a zero the number is even
        if ((tags[speid] >> i) % 2 == 0)
            {
            tags[speid] |= bit_tag << i; // set the bit found to 1
            return i;
            }
        }
    return MOC_ERR_INTERN;
    }

int moc_tag_release(unsigned int speid, int tag)
    {
    if ((speid > 8) || (tag < 0) || (tag > 14))
        return MOC_ERR_INTERN;
    unsigned short bit_tag = 1;
    bit_tag = bit_tag << tag; // translate the tag X to the bitmask with a 1 on only the Xth position
    bit_tag = ~bit_tag; // invert it so the position can be removed by bitwise AND
    tags[speid] &= bit_tag;
    return MOC_SUCCESS;
    }

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