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On EN7581 + MT7996 that change regresses probe: the mailbox completes successfully, but WLAN_FUNC_GET_WAIT_NPU_VERSION still reads as 0.0 and mt76 never binds NPU offload. Healthy boards report 0.1111. Mailbox messages are tiny and already copied by the caller. Bounce through dma_alloc_coherent() so the CPU observes the NPU-written response without relying on streaming DMA direction. Verified on Quantum Fiber W1700K (EN7581 + MT7996). Fixes: 6f884eb87a79 ("net: airoha: Fix DMA direction for NPU mailbox buffer") Assisted-by: Cursor:composer-2 Signed-off-by: Daniel Pawlik --- drivers/net/ethernet/airoha/airoha_npu.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/drivers/net/ethernet/airoha/airoha_npu.c b/drivers/net/ethernet/airoha/airoha_npu.c index b679bed952de..d2f6c9c084b8 100644 --- a/drivers/net/ethernet/airoha/airoha_npu.c +++ b/drivers/net/ethernet/airoha/airoha_npu.c @@ -166,12 +166,21 @@ static int airoha_npu_send_msg(struct airoha_npu *npu, int func_id, u16 core = 0; /* FIXME */ u32 val, offset = core << 4; dma_addr_t dma_addr; + void *dma_buf; int ret; - dma_addr = dma_map_single(npu->dev, p, size, DMA_BIDIRECTIONAL); - ret = dma_mapping_error(npu->dev, dma_addr); - if (ret) - return ret; + /* + * Mailbox payloads are small and bidirectional (CPU sets the + * request, NPU writes the response). Streaming DMA_BIDIRECTIONAL + * mapping regresses EN7581+MT7996: MBOX reports success but + * WLAN_FUNC_GET_WAIT_NPU_VERSION still reads as 0.0. Use a + * coherent bounce buffer so the CPU always sees the NPU response. + */ + dma_buf = dma_alloc_coherent(npu->dev, size, &dma_addr, GFP_ATOMIC); + if (!dma_buf) + return -ENOMEM; + + memcpy(dma_buf, p, size); spin_lock_bh(&npu->cores[core].lock); @@ -191,7 +200,9 @@ static int airoha_npu_send_msg(struct airoha_npu *npu, int func_id, spin_unlock_bh(&npu->cores[core].lock); - dma_unmap_single(npu->dev, dma_addr, size, DMA_BIDIRECTIONAL); + if (!ret) + memcpy(p, dma_buf, size); + dma_free_coherent(npu->dev, size, dma_buf, dma_addr); return ret; } -- 2.55.0