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Thu, 06 Aug 2026 00:26:16 -0700 (PDT) Received: from fedora ([46.205.219.211]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47ff7b25b4asm3900021f8f.26.2026.08.06.00.26.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Aug 2026 00:26:15 -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 v2] net: airoha: npu: use coherent DMA for mailbox messages Date: Thu, 6 Aug 2026 09:26:01 +0200 Message-ID: <20260806072601.1815487-1-pawlik.dan@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260805070851.2885888-1-pawlik.dan@gmail.com> References: <20260805070851.2885888-1-pawlik.dan@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. airoha_npu_send_msg() is also used from PPE foe_commit under spin_lock_bh(), so per-message dma_alloc_coherent(GFP_ATOMIC) is a poor fit. Allocate one device-managed coherent bounce buffer at probe and reuse it under the existing per-core mailbox lock. That also keeps the buffer valid if the NPU completes a write after a mailbox timeout. Verified on Quantum Fiber / Gemtek W1700K (EN7581 + MT7996). Fixes: 6f884eb87a79 ("net: airoha: Fix DMA direction for NPU mailbox buffer") Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20260805070851.2885888-1-pawlik.dan@gmail.com/ Assisted-by: Cursor:composer-2 Signed-off-by: Daniel Pawlik --- v2: - allocate one coherent mailbox buffer at probe and reuse it under the per-core lock instead of per-message dma_alloc_coherent(GFP_ATOMIC) drivers/net/ethernet/airoha/airoha_npu.c | 31 +++++++++++++++++------ include/linux/soc/airoha/airoha_offload.h | 4 +++ 2 files changed, 27 insertions(+), 8 deletions(-) diff --git a/drivers/net/ethernet/airoha/airoha_npu.c b/drivers/net/ethernet/airoha/airoha_npu.c index b679bed952de..dfa09fed907e 100644 --- a/drivers/net/ethernet/airoha/airoha_npu.c +++ b/drivers/net/ethernet/airoha/airoha_npu.c @@ -23,6 +23,8 @@ #define NPU_EN7581_FIRMWARE_RV32_MAX_SIZE 0x200000 #define NPU_EN7581_FIRMWARE_DATA_MAX_SIZE 0x10000 #define NPU_DUMP_SIZE 512 +/* Enough for struct ppe_mbox_data and small WLAN TLV payloads */ +#define AIROHA_NPU_MBOX_SIZE 256 #define REG_NPU_LOCAL_SRAM 0x0 @@ -165,17 +167,24 @@ 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; 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; + if (size > AIROHA_NPU_MBOX_SIZE) + return -EINVAL; + /* + * Mailbox payloads are bidirectional (CPU request, NPU response). + * On EN7581+MT7996, streaming DMA_BIDIRECTIONAL against the + * caller kzalloc() buffer can leave WLAN_FUNC_GET_WAIT_NPU_VERSION + * reading as 0.0 despite MBOX success. Reuse a probe-time coherent + * bounce buffer under the per-core lock (also used from PPE + * foe_commit under atomic context). + */ spin_lock_bh(&npu->cores[core].lock); - regmap_write(npu->regmap, REG_CR_MBQ0_CTRL(0) + offset, dma_addr); + memcpy(npu->mbox_buf, p, size); + + regmap_write(npu->regmap, REG_CR_MBQ0_CTRL(0) + offset, npu->mbox_dma); regmap_write(npu->regmap, REG_CR_MBQ0_CTRL(1) + offset, size); regmap_read(npu->regmap, REG_CR_MBQ0_CTRL(2) + offset, &val); regmap_write(npu->regmap, REG_CR_MBQ0_CTRL(2) + offset, val + 1); @@ -189,9 +198,10 @@ static int airoha_npu_send_msg(struct airoha_npu *npu, int func_id, if (!ret && FIELD_GET(MBOX_MSG_STATUS, val) != NPU_MBOX_SUCCESS) ret = -EINVAL; - spin_unlock_bh(&npu->cores[core].lock); + if (!ret) + memcpy(p, npu->mbox_buf, size); - dma_unmap_single(npu->dev, dma_addr, size, DMA_BIDIRECTIONAL); + spin_unlock_bh(&npu->cores[core].lock); return ret; } @@ -770,6 +780,11 @@ static int airoha_npu_probe(struct platform_device *pdev) if (err) return err; + npu->mbox_buf = dmam_alloc_coherent(dev, AIROHA_NPU_MBOX_SIZE, + &npu->mbox_dma, GFP_KERNEL); + if (!npu->mbox_buf) + return -ENOMEM; + err = airoha_npu_run_firmware(dev, base, &res); if (err) return dev_err_probe(dev, err, "failed to run npu firmware\n"); diff --git a/include/linux/soc/airoha/airoha_offload.h b/include/linux/soc/airoha/airoha_offload.h index 7589fccfeef6..afd481233489 100644 --- a/include/linux/soc/airoha/airoha_offload.h +++ b/include/linux/soc/airoha/airoha_offload.h @@ -179,6 +179,10 @@ struct airoha_npu { struct airoha_foe_stats __iomem *stats; + /* Coherent bounce buffer for mailbox cmd/rsp (airoha_npu_send_msg) */ + void *mbox_buf; + dma_addr_t mbox_dma; + struct { int (*ppe_init)(struct airoha_npu *npu); int (*ppe_deinit)(struct airoha_npu *npu); -- 2.55.0