1.. SPDX-License-Identifier: GPL-2.0-only 2 3.. Copyright (C) 2020-21 Intel Corporation 4 5.. _t7xx_driver_doc: 6 7============================================ 8t7xx driver for MTK PCIe based T700 5G modem 9============================================ 10The t7xx driver is a WWAN PCIe host driver developed for linux or Chrome OS platforms 11for data exchange over PCIe interface between Host platform & MediaTek's T700 5G modem. 12The driver exposes an interface conforming to the MBIM protocol [1]. Any front end 13application (e.g. Modem Manager) could easily manage the MBIM interface to enable 14data communication towards WWAN. The driver also provides an interface to interact 15with the MediaTek's modem via AT commands. 16 17Basic usage 18=========== 19MBIM & AT functions are inactive when unmanaged. The t7xx driver provides 20WWAN port userspace interfaces representing MBIM & AT control channels and does 21not play any role in managing their functionality. It is the job of a userspace 22application to detect port enumeration and enable MBIM & AT functionalities. 23 24Examples of few such userspace applications are: 25 26- mbimcli (included with the libmbim [2] library), and 27- Modem Manager [3] 28 29Management Applications to carry out below required actions for establishing 30MBIM IP session: 31 32- open the MBIM control channel 33- configure network connection settings 34- connect to network 35- configure IP network interface 36 37Management Applications to carry out below required actions for send an AT 38command and receive response: 39 40- open the AT control channel using a UART tool or a special user tool 41 42Management application development 43================================== 44The driver and userspace interfaces are described below. The MBIM protocol is 45described in [1] Mobile Broadband Interface Model v1.0 Errata-1. 46 47MBIM control channel userspace ABI 48---------------------------------- 49 50/dev/wwan0mbim0 character device 51~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 52The driver exposes an MBIM interface to the MBIM function by implementing 53MBIM WWAN Port. The userspace end of the control channel pipe is a 54/dev/wwan0mbim0 character device. Application shall use this interface for 55MBIM protocol communication. 56 57Fragmentation 58~~~~~~~~~~~~~ 59The userspace application is responsible for all control message fragmentation 60and defragmentation as per MBIM specification. 61 62/dev/wwan0mbim0 write() 63~~~~~~~~~~~~~~~~~~~~~~~ 64The MBIM control messages from the management application must not exceed the 65negotiated control message size. 66 67/dev/wwan0mbim0 read() 68~~~~~~~~~~~~~~~~~~~~~~ 69The management application must accept control messages of up the negotiated 70control message size. 71 72MBIM data channel userspace ABI 73------------------------------- 74 75wwan0-X network device 76~~~~~~~~~~~~~~~~~~~~~~ 77The t7xx driver exposes IP link interface "wwan0-X" of type "wwan" for IP 78traffic. Iproute network utility is used for creating "wwan0-X" network 79interface and for associating it with MBIM IP session. 80 81The userspace management application is responsible for creating new IP link 82prior to establishing MBIM IP session where the SessionId is greater than 0. 83 84For example, creating new IP link for a MBIM IP session with SessionId 1: 85 86 ip link add dev wwan0-1 parentdev wwan0 type wwan linkid 1 87 88The driver will automatically map the "wwan0-1" network device to MBIM IP 89session 1. 90 91AT port userspace ABI 92---------------------------------- 93 94/dev/wwan0at0 character device 95~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 96The driver exposes an AT port by implementing AT WWAN Port. 97The userspace end of the control port is a /dev/wwan0at0 character 98device. Application shall use this interface to issue AT commands. 99 100The MediaTek's T700 modem supports the 3GPP TS 27.007 [4] specification. 101 102References 103========== 104[1] *MBIM (Mobile Broadband Interface Model) Errata-1* 105 106- https://www.usb.org/document-library/ 107 108[2] *libmbim "a glib-based library for talking to WWAN modems and devices which 109speak the Mobile Interface Broadband Model (MBIM) protocol"* 110 111- http://www.freedesktop.org/wiki/Software/libmbim/ 112 113[3] *Modem Manager "a DBus-activated daemon which controls mobile broadband 114(2G/3G/4G/5G) devices and connections"* 115 116- http://www.freedesktop.org/wiki/Software/ModemManager/ 117 118[4] *Specification # 27.007 - 3GPP* 119 120- https://www.3gpp.org/DynaReport/27007.htm 121
