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Wed, 05 Aug 2026 00:09:43 -0700 (PDT) Received: from fedora ([46.205.219.119]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4994e4c32e0sm35567225e9.0.2026.08.05.00.09.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Aug 2026 00:09:43 -0700 (PDT) From: Daniel Pawlik To: netdev@vger.kernel.org Cc: lorenzo@kernel.org, win847@gmail.com, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, Daniel Pawlik Subject: [PATCH] net: airoha: npu: use coherent DMA for mailbox messages Date: Wed, 5 Aug 2026 09:08:51 +0200 Message-ID: <20260805070851.2885888-1-pawlik.dan@gmail.com> X-Mailer: git-send-email 2.55.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260805_000946_704945_8B39F499 X-CRM114-Status: GOOD ( 12.69 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Commit 6f884eb87a79 ("net: airoha: Fix DMA direction for NPU mailbox buffer") switched airoha_npu_send_msg() to DMA_BIDIRECTIONAL so non-coherent CPUs invalidate caches before reading NPU GET responses. 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