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b=XJFEMVXVBYc8oUtPxnvxLQHKIuNd8vioUUZR9HLyU7dSoARktS07PYJfKTbwPZ+h/DjmqVyoHzeLj1G6nRDc6jyhhknMZK4odohkRnftwznBwgqcqVQ/nERqKrimNF212yeXv7NKqky8pwysdk913hcPjxyVWpDlyr9bXj8d/v2rsE/DjpvLLYWPvWhABWNwSlEuhneAN/6Yuh8IF/luOR+YUpXZnja8S28Pdj/kvvaGFWErkoMLxnyixe6xGVrmM/8uHvM7NiPauayvl90OJukxncjeuhNP7Kg5F5nH67OKoe9TXAv5y6yyM91viXjcFfSNtsTOIH8YWevPmSHl4g== Authentication-Results: mx.microsoft.com 1; dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=opengear.com; Received: from MWHPR1001MB2095.namprd10.prod.outlook.com (2603:10b6:301:32::34) by SJ5PPF1849371D1.namprd10.prod.outlook.com (2603:10b6:a0f:fc02::78e) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.496.14; Tue, 6 Oct 2026 04:04:29 +0000 Received: from MWHPR1001MB2095.namprd10.prod.outlook.com ([fe80::3933:62ac:2729:f017]) by MWHPR1001MB2095.namprd10.prod.outlook.com ([fe80::3933:62ac:2729:f017%7]) with mapi id 15.21.0496.010; Tue, 6 Oct 2026 04:04:29 +0000 From: Peter Hunt To: loic.poulain@oss.qualcomm.com, ryazanov.s.a@gmail.com Cc: johannes@sipsolutions.net, mani@kernel.org, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org, mhi@lists.linux.dev, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Hunt Subject: [PATCH net-next v7 2/2] net: wwan: mhi_wwan_ctrl: drive DTR/RTS via the IP_CTRL channel Date: Mon, 5 Oct 2026 22:04:22 -0600 Message-ID: <20261006040422.3208888-3-peter.hunt@opengear.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261006040422.3208888-1-peter.hunt@opengear.com> References: <20261006040422.3208888-1-peter.hunt@opengear.com> Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: SJ0PR05CA0157.namprd05.prod.outlook.com (2603:10b6:a03:339::12) To MWHPR1001MB2095.namprd10.prod.outlook.com (2603:10b6:301:32::34) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MWHPR1001MB2095:EE_|SJ5PPF1849371D1:EE_ X-MS-Office365-Filtering-Correlation-Id: 06f32efc-d525-432e-9c49-08df235eeb37 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|23010399003|376014|7416014|18002099003|22082099003|11063799006|56012099006|10067099003|6133799003|3023799007; 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Carry the host serial-control lines to the modem over the dedicated IP_CTRL MHI channel, which this module now also binds. IP_CTRL uses a separate mhi_driver with its own callbacks so the AT/QMI/MBIM data path is untouched; the control-channel device for each MHI controller is tracked in a small registry so an AT port drives the IP_CTRL channel of its own modem (multiple modems are supported). The IP_CTRL channel has to be declared in the controller's channel config for this driver to bind. For the Sierra EM919x/EM929x this is done by commit 83c29a55b89e ("bus: mhi: host: pci_generic: Add IP_CTRL channel for Sierra EM919x/EM929x") in the MHI tree. On controllers that do not declare IP_CTRL the driver does not bind and ->dtr_rts is a no-op. The wwan core (patch 1) raises DTR/RTS on first open and drops them on last close (if HUPCL is set) for any AT port whose driver implements ->dtr_rts, so no open/close handling is needed here. The new ->dtr_rts op lets userspace assert or de-assert them via TIOCMSET/TIOCMBIC/TIOCMBIS. Received device->host serial state messages are silently discarded; a single recycled sink buffer keeps the IP_CTRL DL ring live so the modem's transmit path does not stall. ->dtr_rts is void, following the tty_port_operations model it is modelled on. Delivery is best-effort: at_data.mdmbits always reflects the committed userspace intent for TIOCMGET regardless of whether the IP_CTRL message was queued, and the next ioctl or open/close cycle will resynchronise the modem state. If requeueing the DL sink buffer fails with a transient -ENOMEM it is retried from a work item, so the DL ring does not stay empty. Signed-off-by: Peter Hunt --- v7: Retry a failed DL sink buffer requeue from a delayed work item on -ENOMEM, and log other failures. Note the dependency on the IP_CTRL channel entry in pci_generic, now in the MHI tree. Both from the Sashiko review of v6 v6: Rebase onto net-next. Allocate the IP_CTRL DL sink buffer separately instead of embedding it in struct mhi_wwan_dtr, so DMA cache maintenance on non-coherent platforms cannot touch neighbouring fields. Do not requeue the sink buffer from the DL callback when the transfer completes with an error (e.g. -ENOTCONN during channel teardown) v5: Implement ->dtr_rts(port, mdmbits) and drive DTR and RTS independently. Pre-queue an RX sink buffer in probe and requeue it in the DL callback so the IP_CTRL DL ring does not run empty and stall the modem's transmit path v4: Add dev_dbg when IP_CTRL channel is not enumerated for this controller and when mhi_queue_buf fails, to aid diagnosis of the "URCs missing" case on controllers that do not declare IP_CTRL v3: Remove is_at_port, implement ->dtr_rts instead of ->tiocmset, open/close DTR raise/drop handled by wwan core (Loic Poulain) --- drivers/net/wwan/mhi_wwan_ctrl.c | 239 ++++++++++++++++++++++++++++++- 1 file changed, 238 insertions(+), 1 deletion(-) diff --git a/drivers/net/wwan/mhi_wwan_ctrl.c b/drivers/net/wwan/mhi_wwan_ctrl.c index a31d8540fbb8..feb9c03b6392 100644 --- a/drivers/net/wwan/mhi_wwan_ctrl.c +++ b/drivers/net/wwan/mhi_wwan_ctrl.c @@ -1,8 +1,13 @@ // SPDX-License-Identifier: GPL-2.0-only /* Copyright (c) 2021, Linaro Ltd */ #include +#include #include #include +#include +#include +#include +#include #include /* MHI wwan flags */ @@ -14,6 +19,32 @@ enum mhi_wwan_flags { #define MHI_WWAN_MAX_MTU 0x8000 +/* IP_CTRL channel message that sets the modem's DTR/RTS control lines */ +struct mhi_dtr_ctrl_msg { + __le32 preamble; + __le32 msg_id; + __le32 dest_id; + __le32 size; + __le32 msg; +} __packed; + +#define MHI_DTR_CTRL_MAGIC 0x4C525443 /* 'CTRL' */ +#define MHI_DTR_MSG_DTR BIT(0) +#define MHI_DTR_MSG_RTS BIT(1) +#define MHI_DTR_HOST_STATE 0x10 + +/* Per-controller IP_CTRL channel, used to signal DTR/RTS to that modem */ +struct mhi_wwan_dtr { + struct mhi_controller *cntrl; + struct mhi_device *mhi_dev; + struct list_head node; + struct mhi_dtr_ctrl_msg *rx_buf; /* DL sink, separate allocation for DMA safety */ + struct delayed_work rx_refill; /* retries a failed sink buffer requeue */ +}; + +static LIST_HEAD(mhi_wwan_dtr_list); +static DEFINE_MUTEX(mhi_wwan_dtr_lock); + struct mhi_wwan_dev { /* Lower level is a mhi dev, upper level is a wwan port */ struct mhi_device *mhi_dev; @@ -103,6 +134,61 @@ static void mhi_wwan_ctrl_refill_work(struct work_struct *work) } } +/* Signal the modem's DTR/RTS lines over its own controller's IP_CTRL channel */ +static int mhi_wwan_ctrl_send_dtr(struct mhi_wwan_dev *mhiwwan, unsigned int mdmbits) +{ + struct mhi_controller *cntrl = mhiwwan->mhi_dev->mhi_cntrl; + struct mhi_device *ctrl_dev = NULL; + struct mhi_dtr_ctrl_msg *dtr_msg; + struct mhi_wwan_dtr *dtr; + u32 msg = 0; + int ret; + + guard(mutex)(&mhi_wwan_dtr_lock); + + list_for_each_entry(dtr, &mhi_wwan_dtr_list, node) { + if (dtr->cntrl == cntrl) { + ctrl_dev = dtr->mhi_dev; + break; + } + } + if (!ctrl_dev) { + dev_dbg(&mhiwwan->mhi_dev->dev, + "IP_CTRL not enumerated; DTR/RTS not signalled to modem\n"); + return 0; + } + + dtr_msg = kzalloc_obj(*dtr_msg); + if (!dtr_msg) + return -ENOMEM; + + if (mdmbits & TIOCM_DTR) + msg |= MHI_DTR_MSG_DTR; + if (mdmbits & TIOCM_RTS) + msg |= MHI_DTR_MSG_RTS; + + dtr_msg->preamble = cpu_to_le32(MHI_DTR_CTRL_MAGIC); + dtr_msg->msg_id = cpu_to_le32(MHI_DTR_HOST_STATE); + dtr_msg->dest_id = cpu_to_le32(mhiwwan->mhi_dev->ul_chan_id); + dtr_msg->size = cpu_to_le32(sizeof(__le32)); + dtr_msg->msg = cpu_to_le32(msg); + + ret = mhi_queue_buf(ctrl_dev, DMA_TO_DEVICE, dtr_msg, sizeof(*dtr_msg), + MHI_EOT); + if (ret) { + dev_dbg(&mhiwwan->mhi_dev->dev, + "failed to queue DTR/RTS signal: %d\n", ret); + kfree(dtr_msg); + } + + return ret; +} + +static void mhi_wwan_ctrl_dtr_rts(struct wwan_port *port, unsigned int mdmbits) +{ + mhi_wwan_ctrl_send_dtr(wwan_port_get_drvdata(port), mdmbits); +} + static int mhi_wwan_ctrl_start(struct wwan_port *port) { struct mhi_wwan_dev *mhiwwan = wwan_port_get_drvdata(port); @@ -163,6 +249,7 @@ static const struct wwan_port_ops wwan_pops = { .start = mhi_wwan_ctrl_start, .stop = mhi_wwan_ctrl_stop, .tx = mhi_wwan_ctrl_tx, + .dtr_rts = mhi_wwan_ctrl_dtr_rts, }; static void mhi_ul_xfer_cb(struct mhi_device *mhi_dev, @@ -255,6 +342,118 @@ static void mhi_wwan_ctrl_remove(struct mhi_device *mhi_dev) kfree(mhiwwan); } +/* IP_CTRL channel driver, bound separately so the data-port path is untouched */ +static void mhi_wwan_dtr_ul_xfer_cb(struct mhi_device *mhi_dev, + struct mhi_result *mhi_result) +{ + /* MHI core has done with the buffer, release it */ + kfree(mhi_result->buf_addr); +} + +/* Requeue the single DL sink buffer so the IP_CTRL DL ring never runs empty. + * A transient mapping failure is retried from a work item, other errors mean + * the channel is going away and the next probe queues a fresh buffer. + */ +static void mhi_wwan_dtr_queue_rx(struct mhi_wwan_dtr *dtr) +{ + int ret; + + ret = mhi_queue_buf(dtr->mhi_dev, DMA_FROM_DEVICE, dtr->rx_buf, + sizeof(*dtr->rx_buf), MHI_EOT); + if (ret == -ENOMEM) { + dev_warn_ratelimited(&dtr->mhi_dev->dev, + "failed to requeue IP_CTRL RX buffer, retrying\n"); + schedule_delayed_work(&dtr->rx_refill, msecs_to_jiffies(100)); + } else if (ret) { + dev_dbg(&dtr->mhi_dev->dev, + "failed to requeue IP_CTRL RX buffer: %d\n", ret); + } +} + +static void mhi_wwan_dtr_refill_work(struct work_struct *work) +{ + struct mhi_wwan_dtr *dtr = container_of(to_delayed_work(work), + struct mhi_wwan_dtr, rx_refill); + + mhi_wwan_dtr_queue_rx(dtr); +} + +static void mhi_wwan_dtr_dl_xfer_cb(struct mhi_device *mhi_dev, + struct mhi_result *mhi_result) +{ + struct mhi_wwan_dtr *dtr = dev_get_drvdata(&mhi_dev->dev); + + /* Channel is being torn down (e.g. -ENOTCONN), do not requeue */ + if (mhi_result->transaction_status && + mhi_result->transaction_status != -EOVERFLOW) + return; + + /* Modem serial state not needed, requeue the sink buffer to keep DL ring live */ + mhi_wwan_dtr_queue_rx(dtr); +} + +static int mhi_wwan_dtr_probe(struct mhi_device *mhi_dev, + const struct mhi_device_id *id) +{ + struct mhi_wwan_dtr *dtr; + int ret; + + dtr = kzalloc_obj(*dtr); + if (!dtr) + return -ENOMEM; + + dtr->rx_buf = kmalloc_obj(*dtr->rx_buf); + if (!dtr->rx_buf) { + ret = -ENOMEM; + goto err_free_dtr; + } + INIT_DELAYED_WORK(&dtr->rx_refill, mhi_wwan_dtr_refill_work); + + ret = mhi_prepare_for_transfer(mhi_dev); + if (ret) + goto err_free_buf; + + dtr->cntrl = mhi_dev->mhi_cntrl; + dtr->mhi_dev = mhi_dev; + dev_set_drvdata(&mhi_dev->dev, dtr); + + ret = mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, dtr->rx_buf, + sizeof(*dtr->rx_buf), MHI_EOT); + if (ret) + goto err_unprepare; + + mutex_lock(&mhi_wwan_dtr_lock); + list_add(&dtr->node, &mhi_wwan_dtr_list); + mutex_unlock(&mhi_wwan_dtr_lock); + + return 0; + +err_unprepare: + mhi_unprepare_from_transfer(mhi_dev); +err_free_buf: + kfree(dtr->rx_buf); +err_free_dtr: + kfree(dtr); + return ret; +} + +static void mhi_wwan_dtr_remove(struct mhi_device *mhi_dev) +{ + struct mhi_wwan_dtr *dtr = dev_get_drvdata(&mhi_dev->dev); + + mutex_lock(&mhi_wwan_dtr_lock); + list_del(&dtr->node); + mutex_unlock(&mhi_wwan_dtr_lock); + + mhi_unprepare_from_transfer(mhi_dev); + /* No DL callbacks after unprepare, and a pending retry now fails on + * the disabled channel without rescheduling + */ + cancel_delayed_work_sync(&dtr->rx_refill); + kfree(dtr->rx_buf); + kfree(dtr); +} + static const struct mhi_device_id mhi_wwan_ctrl_match_table[] = { { .chan = "DUN", .driver_data = WWAN_PORT_AT }, { .chan = "DUN2", .driver_data = WWAN_PORT_AT }, @@ -278,7 +477,45 @@ static struct mhi_driver mhi_wwan_ctrl_driver = { }, }; -module_mhi_driver(mhi_wwan_ctrl_driver); +static const struct mhi_device_id mhi_wwan_dtr_match_table[] = { + { .chan = "IP_CTRL" }, + {}, +}; +MODULE_DEVICE_TABLE(mhi, mhi_wwan_dtr_match_table); + +static struct mhi_driver mhi_wwan_dtr_driver = { + .id_table = mhi_wwan_dtr_match_table, + .remove = mhi_wwan_dtr_remove, + .probe = mhi_wwan_dtr_probe, + .ul_xfer_cb = mhi_wwan_dtr_ul_xfer_cb, + .dl_xfer_cb = mhi_wwan_dtr_dl_xfer_cb, + .driver = { + .name = "mhi_wwan_dtr", + }, +}; + +static int __init mhi_wwan_ctrl_init(void) +{ + int ret; + + ret = mhi_driver_register(&mhi_wwan_dtr_driver); + if (ret) + return ret; + + ret = mhi_driver_register(&mhi_wwan_ctrl_driver); + if (ret) + mhi_driver_unregister(&mhi_wwan_dtr_driver); + + return ret; +} +module_init(mhi_wwan_ctrl_init); + +static void __exit mhi_wwan_ctrl_exit(void) +{ + mhi_driver_unregister(&mhi_wwan_ctrl_driver); + mhi_driver_unregister(&mhi_wwan_dtr_driver); +} +module_exit(mhi_wwan_ctrl_exit); MODULE_LICENSE("GPL v2"); MODULE_DESCRIPTION("MHI WWAN CTRL Driver"); -- 2.43.0