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Sat, 24 Oct 2026 08:42:20 -0700 (PDT) Received: from plex ([2406:6d00:a27c:4200:aab8:e0ff:fe02:33c1]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-369e8daf444sm7766450eec.18.2026.10.24.08.42.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 24 Oct 2026 08:42:20 -0700 (PDT) From: Chris Scott To: netdev@vger.kernel.org Cc: lorenzo@kernel.org, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@kernel.org, kuba@kernel.org, pabeni@redhat.com, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, matthias.bgg@gmail.com, angelogioacchino.delregno@collabora.com, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, pawlik.dan@gmail.com, zhengping.zhang@airoha.com, Chris Scott Subject: [RFC net-next 3/3] net: airoha: npu: use coherent memory for mailbox messages Date: Sun, 25 Oct 2026 01:41:50 +1000 Message-ID: <20261024154150.45733-4-gilroyscott1970@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261024154150.45733-1-gilroyscott1970@gmail.com> References: <20261024154150.45733-1-gilroyscott1970@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Daniel Pawlik airoha_npu_send_msg() maps the caller's kzalloc() buffer with DMA_BIDIRECTIONAL. These buffers are small and not cacheline aligned, so on arm64 the mapping bounces through swiotlb. On a 2 GiB EN7581 board the default swiotlb pool sits above 0xc0000000 (0xff6cf000 on W1700K), outside the 0x80000000-0xbfffffff window the NPU can address; higher addresses alias the lower 1 GiB. On W1700K + MT7996 this makes WLAN_FUNC_GET_WAIT_NPU_VERSION read back 0.0 and mt76 does not bind NPU offload. Allocate one coherent buffer per NPU core at probe and reuse it under the per-core mailbox lock. With the previous patch it comes from the NPU DMA pool, inside the window. airoha_npu_send_msg() is also called from PPE foe_commit under spin_lock_bh(), which rules out a per-message GFP_ATOMIC coherent allocation. Add __airoha_npu_send_msg() with an optional reply buffer so GET callers copy only the trailing response payload; airoha_npu_send_msg() keeps copying the whole buffer back, like the bidirectional mapping. The original version of this patch was written with Cursor (composer-2); it was rebased onto net-next and its commit message rewritten with Claude (Anthropic). Link: https://lore.kernel.org/r/20260809152813.585797-1-pawlik.dan@gmail.com Link: https://lore.kernel.org/r/atCRsquzA1UxSpCc@mediatek.com Signed-off-by: Daniel Pawlik Signed-off-by: Chris Scott --- drivers/net/ethernet/airoha/airoha_npu.c | 65 +++++++++++++++++------ include/linux/soc/airoha/airoha_offload.h | 3 ++ 2 files changed, 51 insertions(+), 17 deletions(-) diff --git a/drivers/net/ethernet/airoha/airoha_npu.c b/drivers/net/ethernet/airoha/airoha_npu.c index 069fd60680..3d1aa63dd5 100644 --- a/drivers/net/ethernet/airoha/airoha_npu.c +++ b/drivers/net/ethernet/airoha/airoha_npu.c @@ -24,6 +24,12 @@ #define NPU_EN7581_FIRMWARE_RV32_MAX_SIZE 0x200000 #define NPU_EN7581_FIRMWARE_DATA_MAX_SIZE 0x10000 #define NPU_DUMP_SIZE 512 +/* + * Mailbox DMA payload size. Covers sizeof(struct ppe_mbox_data) (28) and + * WLAN TLV messages (header + payload); largest in-tree WLAN payload today + * is 16 bytes (INODE_TXRX_REG_ADDR). Keep headroom for future commands. + */ +#define AIROHA_NPU_MBOX_SIZE 256 #define REG_NPU_LOCAL_SRAM 0x0 @@ -161,23 +167,32 @@ struct wlan_mbox_data { DECLARE_FLEX_ARRAY(u8, d); }; -static int airoha_npu_send_msg(struct airoha_npu *npu, int func_id, - void *p, int size) +static int __airoha_npu_send_msg(struct airoha_npu *npu, int func_id, + const void *data, int len, void *reply, + u16 reply_len) { - u16 core = 0; /* FIXME */ - u32 val, offset = core << 4; - dma_addr_t dma_addr; + struct airoha_npu_core *core = &npu->cores[0]; /* FIXME: core */ + u32 val, offset = 0; 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 (len > AIROHA_NPU_MBOX_SIZE) + return -EINVAL; + + if (reply && reply_len > len) + return -EINVAL; + + /* + * The NPU only reaches DRAM at 0x80000000-0xbfffffff; a streaming + * mapping of the caller buffer may bounce through swiotlb outside + * that window. Use the probe-time coherent buffer, which comes from + * the NPU DMA pool when one is declared. + */ + spin_lock_bh(&core->lock); - spin_lock_bh(&npu->cores[core].lock); + memcpy(core->buf, data, len); - regmap_write(npu->regmap, REG_CR_MBQ0_CTRL(0) + offset, dma_addr); - regmap_write(npu->regmap, REG_CR_MBQ0_CTRL(1) + offset, size); + regmap_write(npu->regmap, REG_CR_MBQ0_CTRL(0) + offset, core->addr); + regmap_write(npu->regmap, REG_CR_MBQ0_CTRL(1) + offset, len); regmap_read(npu->regmap, REG_CR_MBQ0_CTRL(2) + offset, &val); regmap_write(npu->regmap, REG_CR_MBQ0_CTRL(2) + offset, val + 1); val = FIELD_PREP(MBOX_MSG_FUNC_ID, func_id) | MBOX_MSG_WAIT_RSP; @@ -190,13 +205,21 @@ 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); + /* Copy the trailing reply_len bytes of the response. */ + if (!ret && reply) + memcpy(reply, core->buf + len - reply_len, reply_len); - dma_unmap_single(npu->dev, dma_addr, size, DMA_BIDIRECTIONAL); + spin_unlock_bh(&core->lock); return ret; } +static int airoha_npu_send_msg(struct airoha_npu *npu, int func_id, + void *data, int len) +{ + return __airoha_npu_send_msg(npu, func_id, data, len, data, len); +} + static int airoha_npu_load_firmware(struct device *dev, void __iomem *addr, const char *fw_name, int fw_max_size) { @@ -500,9 +523,8 @@ static int airoha_npu_wlan_msg_get(struct airoha_npu *npu, int ifindex, wlan_data->func_type = NPU_OP_GET; wlan_data->func_id = func_id; - err = airoha_npu_send_msg(npu, NPU_FUNC_WIFI, wlan_data, len); - if (!err) - memcpy(data, wlan_data->d, data_len); + err = __airoha_npu_send_msg(npu, NPU_FUNC_WIFI, wlan_data, len, + data, data_len); kfree(wlan_data); return err; @@ -794,6 +816,15 @@ static int airoha_npu_probe(struct platform_device *pdev) return err; } + for (i = 0; i < ARRAY_SIZE(npu->cores); i++) { + struct airoha_npu_core *core = &npu->cores[i]; + + core->buf = dmam_alloc_coherent(dev, AIROHA_NPU_MBOX_SIZE, + &core->addr, GFP_KERNEL); + if (!core->buf) + return -ENOMEM; + } + err = airoha_npu_run_firmware(dev, base, &res); if (err) return err; diff --git a/include/linux/soc/airoha/airoha_offload.h b/include/linux/soc/airoha/airoha_offload.h index 7589fccfee..16a988ad74 100644 --- a/include/linux/soc/airoha/airoha_offload.h +++ b/include/linux/soc/airoha/airoha_offload.h @@ -173,6 +173,9 @@ struct airoha_npu { /* protect concurrent npu memory accesses */ spinlock_t lock; struct work_struct wdt_work; + /* Coherent bounce buffer for mailbox cmd/rsp */ + void *buf; + dma_addr_t addr; } cores[NPU_NUM_CORES]; int irqs[NPU_NUM_IRQ]; -- 2.53.0