[PATCH net-next v8 2/2] net: Add Qcom WWAN control driver

Loic Poulain
2021-04-02T13:58:32Z

The MHI WWWAN control driver allows MHI QCOM-based modems to expose
different modem control protocols/ports via the WWAN framework, so that
userspace modem tools or daemon (e.g. ModemManager) can control WWAN
config and state (APN config, SMS, provider selection...). A QCOM-based
modem can expose one or several of the following protocols:
- AT: Well known AT commands interactive protocol (microcom, minicom...)
- MBIM: Mobile Broadband Interface Model (libmbim, mbimcli)
- QMI: QCOM MSM/Modem Interface (libqmi, qmicli)
- QCDM: QCOM Modem diagnostic interface (libqcdm)
- FIREHOSE: XML-based protocol for Modem firmware management
(qmi-firmware-update)

Note that this patch is mostly a rework of the earlier MHI UCI
tentative that was a generic interface for accessing MHI bus from
userspace. As suggested, this new version is WWAN specific and is
dedicated to only expose channels used for controlling a modem, and
for which related opensource userpace support exist.

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
---
v2: update copyright (2021)
v3: Move driver to dedicated drivers/net/wwan directory
v4: Rework to use wwan framework instead of self cdev management
v5: Fix errors/typos in Kconfig
v6: - Move to new wwan interface, No need dedicated call to wwan_dev_create
- Cleanup code (remove legacy from mhi_uci, unused defines/vars...)
- Remove useless write_lock mutex
- Add mhi_wwan_wait_writable and mhi_wwan_wait_dlqueue_lock_irq helpers
- Rework locking
- Add MHI_WWAN_TX_FULL flag
- Add support for NONBLOCK read/write
v7: Fix change log (mixed up 1/2 and 2/2)
v8: - Implement wwan_port_ops (instead of fops)
- Remove all mhi wwan data obsolete members (kref, lock, waitqueues)
- Add tracking of RX buffer budget
- Use WWAN TX flow control function to stop TX when MHI queue is full

drivers/net/wwan/Kconfig | 14 +++
drivers/net/wwan/Makefile | 2 +
drivers/net/wwan/mhi_wwan_ctrl.c | 253 +++++++++++++++++++++++++++++++++++++++
3 files changed, 269 insertions(+)
create mode 100644 drivers/net/wwan/mhi_wwan_ctrl.c

diff --git a/drivers/net/wwan/Kconfig b/drivers/net/wwan/Kconfig
index 545fe54..ce0bbfb 100644
--- a/drivers/net/wwan/Kconfig
+++ b/drivers/net/wwan/Kconfig
@@ -19,4 +19,18 @@ config WWAN_CORE
To compile this driver as a module, choose M here: the module will be
called wwan.

+config MHI_WWAN_CTRL
+ tristate "MHI WWAN control driver for QCOM-based PCIe modems"
+ select WWAN_CORE
+ depends on MHI_BUS
+ help
+ MHI WWAN CTRL allows QCOM-based PCIe modems to expose different modem
+ control protocols/ports to userspace, including AT, MBIM, QMI, DIAG
+ and FIREHOSE. These protocols can be accessed directly from userspace
+ (e.g. AT commands) or via libraries/tools (e.g. libmbim, libqmi,
+ libqcdm...).
+
+ To compile this driver as a module, choose M here: the module will be
+ called mhi_wwan_ctrl
+
endif # WWAN
diff --git a/drivers/net/wwan/Makefile b/drivers/net/wwan/Makefile
index 934590b..556cd90 100644
--- a/drivers/net/wwan/Makefile
+++ b/drivers/net/wwan/Makefile
@@ -5,3 +5,5 @@

obj-$(CONFIG_WWAN_CORE) += wwan.o
wwan-objs += wwan_core.o
+
+obj-$(CONFIG_MHI_WWAN_CTRL) += mhi_wwan_ctrl.o
diff --git a/drivers/net/wwan/mhi_wwan_ctrl.c b/drivers/net/wwan/mhi_wwan_ctrl.c
new file mode 100644
index 0000000..f2fab23
--- /dev/null
+++ b/drivers/net/wwan/mhi_wwan_ctrl.c
@@ -0,0 +1,253 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2021, Linaro Ltd <loic.poulain@linaro.org> */
+#include <linux/kernel.h>
+#include <linux/mhi.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/wwan.h>
+
+/* MHI wwan flags */
+#define MHI_WWAN_DL_CAP BIT(0)
+#define MHI_WWAN_UL_CAP BIT(1)
+#define MHI_WWAN_STARTED BIT(2)
+
+#define MHI_WWAN_MAX_MTU 0x8000
+
+struct mhi_wwan_dev {
+ /* Lower level is a mhi dev, upper level is a wwan port */
+ struct mhi_device *mhi_dev;
+ struct wwan_port *wwan_port;
+
+ /* State and capabilities */
+ unsigned long flags;
+ size_t mtu;
+
+ /* Protect against concurrent TX and TX-completion (bh) */
+ spinlock_t tx_lock;
+
+ struct work_struct rx_refill;
+ atomic_t rx_budget;
+};
+
+static bool mhi_wwan_ctrl_refill_needed(struct mhi_wwan_dev *mhiwwan)
+{
+ if (!test_bit(MHI_WWAN_STARTED, &mhiwwan->flags))
+ return false;
+
+ if (!test_bit(MHI_WWAN_DL_CAP, &mhiwwan->flags))
+ return false;
+
+ if (!atomic_read(&mhiwwan->rx_budget))
+ return false;
+
+ return true;
+}
+
+void __mhi_skb_destructor(struct sk_buff *skb)
+{
+ struct mhi_wwan_dev *mhiwwan = skb_shinfo(skb)->destructor_arg;
+
+ /* RX buffer has been consumed, increase the allowed budget */
+ atomic_inc(&mhiwwan->rx_budget);
+
+ if (mhi_wwan_ctrl_refill_needed(mhiwwan))
+ schedule_work(&mhiwwan->rx_refill);
+}
+
+static void mhi_wwan_ctrl_refill_work(struct work_struct *work)
+{
+ struct mhi_wwan_dev *mhiwwan = container_of(work, struct mhi_wwan_dev, rx_refill);
+ struct mhi_device *mhi_dev = mhiwwan->mhi_dev;
+
+ if (!mhi_wwan_ctrl_refill_needed(mhiwwan))
+ return;
+
+ while (atomic_read(&mhiwwan->rx_budget)) {
+ struct sk_buff *skb;
+
+ skb = alloc_skb(mhiwwan->mtu, GFP_KERNEL);
+ if (!skb)
+ break;
+
+ /* To prevent unlimited buffer allocation if nothing consumes
+ * the RX buffers (passed to WWAN core), track their lifespan
+ * to not allocate more than allowed budget.
+ */
+ skb->destructor = __mhi_skb_destructor;
+ skb_shinfo(skb)->destructor_arg = mhiwwan;
+
+ if (mhi_queue_skb(mhi_dev, DMA_FROM_DEVICE, skb, mhiwwan->mtu, MHI_EOT)) {
+ dev_err(&mhi_dev->dev, "Failed to queue buffer\n");
+ kfree_skb(skb);
+ break;
+ }
+
+ atomic_dec(&mhiwwan->rx_budget);
+ }
+}
+
+static int mhi_wwan_ctrl_start(struct wwan_port *port)
+{
+ struct mhi_wwan_dev *mhiwwan = wwan_port_get_drvdata(port);
+ int ret, rx_budget;
+
+ /* Start mhi device's channel(s) */
+ ret = mhi_prepare_for_transfer(mhiwwan->mhi_dev);
+ if (ret)
+ return ret;
+
+ set_bit(MHI_WWAN_STARTED, &mhiwwan->flags);
+
+ /* Don't allocate more buffers than MHI channel queue size */
+ rx_budget = mhi_get_free_desc_count(mhiwwan->mhi_dev, DMA_FROM_DEVICE);
+ atomic_set(&mhiwwan->rx_budget, rx_budget);
+
+ /* Add buffers to the MHI inbound queue */
+ mhi_wwan_ctrl_refill_work(&mhiwwan->rx_refill);
+
+ return 0;
+}
+
+static void mhi_wwan_ctrl_stop(struct wwan_port *port)
+{
+ struct mhi_wwan_dev *mhiwwan = wwan_port_get_drvdata(port);
+
+ clear_bit(MHI_WWAN_STARTED, &mhiwwan->flags);
+ mhi_unprepare_from_transfer(mhiwwan->mhi_dev);
+}
+
+static int mhi_wwan_ctrl_tx(struct wwan_port *port, struct sk_buff *skb)
+{
+ struct mhi_wwan_dev *mhiwwan = wwan_port_get_drvdata(port);
+ int ret;
+
+ if (skb->len > mhiwwan->mtu)
+ return -EMSGSIZE;
+
+ if (!test_bit(MHI_WWAN_UL_CAP, &mhiwwan->flags))
+ return -ENOTSUPP;
+
+ spin_lock_bh(&mhiwwan->tx_lock);
+ ret = mhi_queue_skb(mhiwwan->mhi_dev, DMA_TO_DEVICE, skb, skb->len, MHI_EOT);
+ if (mhi_queue_is_full(mhiwwan->mhi_dev, DMA_TO_DEVICE))
+ wwan_port_txoff(port);
+ spin_unlock_bh(&mhiwwan->tx_lock);
+
+ return ret;
+}
+
+static const struct wwan_port_ops wwan_pops = {
+ .start = mhi_wwan_ctrl_start,
+ .stop = mhi_wwan_ctrl_stop,
+ .tx = mhi_wwan_ctrl_tx,
+};
+
+static void mhi_ul_xfer_cb(struct mhi_device *mhi_dev,
+ struct mhi_result *mhi_result)
+{
+ struct mhi_wwan_dev *mhiwwan = dev_get_drvdata(&mhi_dev->dev);
+ struct wwan_port *port = mhiwwan->wwan_port;
+ struct sk_buff *skb = mhi_result->buf_addr;
+
+ dev_dbg(&mhi_dev->dev, "%s: status: %d xfer_len: %zu\n", __func__,
+ mhi_result->transaction_status, mhi_result->bytes_xferd);
+
+ /* MHI core has done with the buffer, release it */
+ consume_skb(skb);
+
+ spin_lock_bh(&mhiwwan->tx_lock);
+ if (!mhi_queue_is_full(mhiwwan->mhi_dev, DMA_TO_DEVICE))
+ wwan_port_txon(port);
+ spin_unlock_bh(&mhiwwan->tx_lock);
+}
+
+static void mhi_dl_xfer_cb(struct mhi_device *mhi_dev,
+ struct mhi_result *mhi_result)
+{
+ struct mhi_wwan_dev *mhiwwan = dev_get_drvdata(&mhi_dev->dev);
+ struct wwan_port *port = mhiwwan->wwan_port;
+ struct sk_buff *skb = mhi_result->buf_addr;
+
+ dev_dbg(&mhi_dev->dev, "%s: status: %d receive_len: %zu\n", __func__,
+ mhi_result->transaction_status, mhi_result->bytes_xferd);
+
+ if (mhi_result->transaction_status &&
+ mhi_result->transaction_status != -EOVERFLOW) {
+ kfree_skb(skb);
+ return;
+ }
+
+ /* MHI core does not update skb->len, do it before forward */
+ skb_put(skb, mhi_result->bytes_xferd);
+ wwan_port_rx(port, skb);
+}
+
+static int mhi_wwan_ctrl_probe(struct mhi_device *mhi_dev,
+ const struct mhi_device_id *id)
+{
+ struct mhi_controller *cntrl = mhi_dev->mhi_cntrl;
+ struct mhi_wwan_dev *mhiwwan;
+
+ mhiwwan = kzalloc(sizeof(*mhiwwan), GFP_KERNEL);
+ if (!mhiwwan)
+ return -ENOMEM;
+
+ mhiwwan->mhi_dev = mhi_dev;
+ mhiwwan->mtu = MHI_WWAN_MAX_MTU;
+ INIT_WORK(&mhiwwan->rx_refill, mhi_wwan_ctrl_refill_work);
+ spin_lock_init(&mhiwwan->tx_lock);
+
+ if (mhi_dev->dl_chan)
+ set_bit(MHI_WWAN_DL_CAP, &mhiwwan->flags);
+ if (mhi_dev->ul_chan)
+ set_bit(MHI_WWAN_UL_CAP, &mhiwwan->flags);
+
+ dev_set_drvdata(&mhi_dev->dev, mhiwwan);
+
+ /* Register as a wwan port, id->driver_data contains wwan port type */
+ mhiwwan->wwan_port = wwan_create_port(&cntrl->mhi_dev->dev,
+ id->driver_data,
+ &wwan_pops, mhiwwan);
+ if (IS_ERR(mhiwwan->wwan_port)) {
+ kfree(mhiwwan);
+ return PTR_ERR(mhiwwan->wwan_port);
+ }
+
+ return 0;
+};
+
+static void mhi_wwan_ctrl_remove(struct mhi_device *mhi_dev)
+{
+ struct mhi_wwan_dev *mhiwwan = dev_get_drvdata(&mhi_dev->dev);
+
+ wwan_remove_port(mhiwwan->wwan_port);
+ cancel_work_sync(&mhiwwan->rx_refill);
+ kfree(mhiwwan);
+}
+
+static const struct mhi_device_id mhi_wwan_ctrl_match_table[] = {
+ { .chan = "DUN", .driver_data = WWAN_PORT_AT },
+ { .chan = "MBIM", .driver_data = WWAN_PORT_MBIM },
+ { .chan = "QMI", .driver_data = WWAN_PORT_QMI },
+ { .chan = "DIAG", .driver_data = WWAN_PORT_QCDM },
+ { .chan = "FIREHOSE", .driver_data = WWAN_PORT_FIREHOSE },
+ {},
+};
+MODULE_DEVICE_TABLE(mhi, mhi_wwan_ctrl_match_table);
+
+static struct mhi_driver mhi_wwan_ctrl_driver = {
+ .id_table = mhi_wwan_ctrl_match_table,
+ .remove = mhi_wwan_ctrl_remove,
+ .probe = mhi_wwan_ctrl_probe,
+ .ul_xfer_cb = mhi_ul_xfer_cb,
+ .dl_xfer_cb = mhi_dl_xfer_cb,
+ .driver = {
+ .name = "mhi_wwan_ctrl",
+ },
+};
+
+module_mhi_driver(mhi_wwan_ctrl_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("MHI WWAN CTRL Driver");
+MODULE_AUTHOR("Loic Poulain <loic.poulain@linaro.org>");
--
2.7.4