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perf(matmul): remove all DMA TAG writes (hardware ignores TAG register)

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Each uncached TAG write costs ~810ns on the AXI bus. Removed:
- 2 TAG writes per main loop iteration (Ch1 store + Ch0 pre-fire)
- 2 TAG writes in prologue (group 0 load + pre-fire group 1)
- 1 TAG write in epilogue (final store)

Total: ~10,000 wasted AXI transactions eliminated for 5000 groups.
Estimated ~8% reduction in per-iteration time.
This commit is contained in:
FallenSigh
2026-06-26 17:49:39 +08:00
parent 07b670b4c9
commit f55e15af32
1 changed files with 0 additions and 5 deletions
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5
sdk/software/examples/asm/user-sample.c
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@@ -94,7 +94,6 @@ int main(void)
ch0->SRC_ADDR = EXTRAM_PHYS_AB(0);
ch0->DST_ADDR = phys_bank_AB[0];
ch0->LENGTH = 128;
ch0->TAG = 10;
ch0->CTRL = DMA_CTRL_VAL;
while (!(ch0->STATUS & STATUS_DONE_BIT)) {}
ch0->STATUS = STATUS_DONE_BIT;
@@ -107,7 +106,6 @@ int main(void)
ch0->SRC_ADDR = EXTRAM_PHYS_AB(1);
ch0->DST_ADDR = phys_bank_AB[1];
ch0->LENGTH = 128;
ch0->TAG = 10;
ch0->CTRL = DMA_CTRL_VAL;
}
@@ -143,7 +141,6 @@ int main(void)
ch1->SRC_ADDR = phys_bank_C[prev_bank];
ch1->DST_ADDR = EXTRAM_PHYS_C(g - 1);
ch1->LENGTH = 192;
ch1->TAG = 20;
ch1->CTRL = DMA_CTRL_VAL;
// 4. Wait for current DMA Ch0 load (group g → cur_bank, pre-fired in iteration g-1)
@@ -160,7 +157,6 @@ int main(void)
ch0->SRC_ADDR = EXTRAM_PHYS_AB(g + 1);
ch0->DST_ADDR = phys_bank_AB[next_bank];
ch0->LENGTH = 128;
ch0->TAG = 10;
ch0->CTRL = DMA_CTRL_VAL;
}
@@ -183,7 +179,6 @@ int main(void)
ch1->SRC_ADDR = phys_bank_C[(MATMUL_GROUP_NUM - 1) % 2];
ch1->DST_ADDR = EXTRAM_PHYS_C(MATMUL_GROUP_NUM - 1);
ch1->LENGTH = 192;
ch1->TAG = 20;
ch1->CTRL = DMA_CTRL_VAL;
while (!(ch1->STATUS & STATUS_DONE_BIT)) {}
ch1->STATUS = STATUS_DONE_BIT;