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[HEXAGON] Split huge 1D DMA Transfers into smaller transfers with leg… #10971

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Apr 12, 2022
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[HEXAGON] Split huge 1D DMA Transfers into smaller transfers with leg… #10971

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31 changes: 30 additions & 1 deletion src/runtime/hexagon/hexagon/hexagon_user_dma.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,7 @@ int init_hexagon_user_dma() {
return DMA_SUCCESS;
}

int hexagon_user_dma_1d_sync(void* dst, void* src, uint32_t length) {
int hexagon_user_dma_1d_sync_helper(void* dst, void* src, uint32_t length) {
#if defined(__hexagon__) && __HEXAGON_ARCH__ >= 68
static int config_dma = init_hexagon_user_dma();
if (config_dma != DMA_SUCCESS) {
Expand Down Expand Up @@ -114,6 +114,35 @@ int hexagon_user_dma_1d_sync(void* dst, void* src, uint32_t length) {
#endif
}

int hexagon_user_dma_1d_sync(void* dst, void* src, uint32_t length) {
// One DMA transfer can copy atmost DESC_LENGTH_MASK bytes.
// Make the common case quick.
if (length <= DESC_LENGTH_MASK) return hexagon_user_dma_1d_sync_helper(dst, src, length);

// Split big transfers into smaller transfers.
char* cast_src = static_cast<char*>(src);
char* cast_dst = static_cast<char*>(dst);
for (uint32_t i = 0; i < length;) {
// Ensure there is no overflow while updating i
uint32_t cur_len = std::min<uint32_t>(length - i, DESC_LENGTH_MASK);
int ret_val = hexagon_user_dma_1d_sync_helper(&cast_dst[i], &cast_src[i], cur_len);
if (ret_val != DMA_SUCCESS) return ret_val;
// 2 cases for new val for i:
// 1. length - i <= DESC_LENGTH_MASK (<= MAX_UINT)
// new_i = i + (length - i) = length, no more iter
// and no overflow (since (length - i) <= (MAX_UINT - i))
// 2. length - i > DESC_LENGTH_MASK
// length > (i + DESC_LENGTH_MASK)
// new_i = (i + DESC_LENGTH_MASK)
// length > new_i for next iter, we're done
// length - i > DESC_LENGTH_MASK
// and length <= MAX_UINT,
// so MAX_UINT >= length > DESC_LEN_MASK + i
// MAX_UINT > (DESC_LEN_MASK + i), so no overflow
i += cur_len;
}
return DMA_SUCCESS;
}
} // namespace hexagon
} // namespace runtime
} // namespace tvm