Commit a212d9f3 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'iosm-driver' 

M Chetan Kumar says:

====================
net: iosm: PCIe Driver for Intel M.2 Modem

The IOSM (IPC over Shared Memory) driver is a PCIe host driver implemented
for linux or chrome platform for data exchange over PCIe interface between
Host platform & Intel M.2 Modem. The driver exposes interface conforming to
the MBIM protocol. Any front end application ( eg: Modem Manager) could
easily manage the MBIM interface to enable data communication towards WWAN.

Intel M.2 modem uses 2 BAR regions. The first region is dedicated to Doorbell
register for IRQs and the second region is used as scratchpad area for book
keeping modem execution stage details along with host system shared memory
region context details. The upper edge of the driver exposes the control and
data channels for user space application interaction. At lower edge these data
and control channels are associated to pipes. The pipes are lowest level
interfaces used over PCIe as a logical channel for message exchange. A single
channel maps to UL and DL pipe and are initialized on device open.

On UL path, driver copies application sent data to SKBs associate it with
transfer descriptor and puts it on to ring buffer for DMA transfer. Once
information has been updated in shared memory region, host gives a Doorbell
to modem to perform DMA and modem uses MSI to communicate back to host.
For receiving data in DL path, SKBs are pre-allocated during pipe open and
transfer descriptors are given to modem for DMA transfer.

The driver exposes two types of ports, namely "wwan0mbim0", a char device node
which is used for MBIM control operation and "wwan0-x",(x = 0,1,2..7) network
interfaces for IP data communication.
1) MBIM Control Interface:
This node exposes an interface between modem and application using char device
exposed by "IOSM" driver to establish and manage the MBIM data communication
with PCIe based Intel M.2 Modems.

2) MBIM Data Interface:
The IOSM driver exposes IP link interface "wwan0-x" of type "wwan" for IP traffic.
Iproute network utility is used for creating "wwan0-x" network interface and for
associating it with MBIM IP session. The Driver supports upto 8 IP sessions for
simultaneous IP communication.

This applies on top of WWAN core rtnetlink series posted here:
https://lore.kernel.org/netdev/1623486057-13075-1-git-send-email-loic.poulain@linaro.org/

Also driver has been compiled and tested on top of netdev net-next tree.
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/


====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents ffbbc5e5 f7af616c

Documentation/networking/device_drivers/index.rst

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@@ -18,6 +18,7 @@ Contents: 
   qlogic/index

   wan/index

   wifi/index

   wwan/index



.. only::  subproject and html

Documentation/networking/device_drivers/wwan/index.rst

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.. SPDX-License-Identifier: GPL-2.0-only



WWAN Device Drivers

===================



Contents:



.. toctree::

   :maxdepth: 2



   iosm



.. only::  subproject and html



   Indices

   =======



   * :ref:`genindex`

Documentation/networking/device_drivers/wwan/iosm.rst

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.. SPDX-License-Identifier: GPL-2.0-only



.. Copyright (C) 2020-21 Intel Corporation



.. _iosm_driver_doc:



===========================================

IOSM Driver for Intel M.2 PCIe based Modems

===========================================

The IOSM (IPC over Shared Memory) driver is a WWAN PCIe host driver developed

for linux or chrome platform for data exchange over PCIe interface between

Host platform & Intel M.2 Modem. The driver exposes interface conforming to the

MBIM protocol [1]. Any front end application ( eg: Modem Manager) could easily

manage the MBIM interface to enable data communication towards WWAN.



Basic usage

===========

MBIM functions are inactive when unmanaged. The IOSM driver only provides a

userspace interface MBIM "WWAN PORT" representing MBIM control channel and does

not play any role in managing the functionality. It is the job of a userspace

application to detect port enumeration and enable MBIM functionality.



Examples of few such userspace application are:

- mbimcli (included with the libmbim [2] library), and

- Modem Manager [3]



Management Applications to carry out below required actions for establishing

MBIM IP session:

- open the MBIM control channel

- configure network connection settings

- connect to network

- configure IP network interface



Management application development

==================================

The driver and userspace interfaces are described below. The MBIM protocol is

described in [1] Mobile Broadband Interface Model v1.0 Errata-1.



MBIM control channel userspace ABI

----------------------------------



/dev/wwan0mbim0 character device

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The driver exposes an MBIM interface to the MBIM function by implementing

MBIM WWAN Port. The userspace end of the control channel pipe is a

/dev/wwan0mbim0 character device. Application shall use this interface for

MBIM protocol communication.



Fragmentation

~~~~~~~~~~~~~

The userspace application is responsible for all control message fragmentation

and defragmentation as per MBIM specification.



/dev/wwan0mbim0 write()

~~~~~~~~~~~~~~~~~~~~~

The MBIM control messages from the management application must not exceed the

negotiated control message size.



/dev/wwan0mbim0 read()

~~~~~~~~~~~~~~~~~~~~

The management application must accept control messages of up the negotiated

control message size.



MBIM data channel userspace ABI

-------------------------------



wwan0-X network device

~~~~~~~~~~~~~~~~~~~~

The IOSM driver exposes IP link interface "wwan0-X" of type "wwan" for IP

traffic. Iproute network utility is used for creating "wwan0-X" network

interface and for associating it with MBIM IP session. The Driver supports

upto 8 IP sessions for simultaneous IP communication.



The userspace management application is responsible for creating new IP link

prior to establishing MBIM IP session where the SessionId is greater than 0.



For example, creating new IP link for a MBIM IP session with SessionId 1:



  ip link add dev wwan0-1 parentdev-name wwan0 type wwan linkid 1



The driver will automatically map the "wwan0-1" network device to MBIM IP

session 1.



References

==========

[1] "MBIM (Mobile Broadband Interface Model) Errata-1"

      - https://www.usb.org/document-library/



[2] libmbim - "a glib-based library for talking to WWAN modems and

      devices which speak the Mobile Interface Broadband Model (MBIM)

      protocol"

      - http://www.freedesktop.org/wiki/Software/libmbim/



[3] Modem Manager - "a DBus-activated daemon which controls mobile

      broadband (2G/3G/4G) devices and connections"

      - http://www.freedesktop.org/wiki/Software/ModemManager/

MAINTAINERS

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@@ -9453,6 +9453,13 @@ L: Dell.Client.Kernel@dell.com 
S:	Maintained

F:	drivers/platform/x86/intel-wmi-thunderbolt.c









INTEL WWAN IOSM DRIVER









M:	M Chetan Kumar <m.chetan.kumar@intel.com>









M:	Intel Corporation <linuxwwan@intel.com>









L:	netdev@vger.kernel.org









S:	Maintained









F:	drivers/net/wwan/iosm/

















INTEL(R) TRACE HUB









M:	Alexander Shishkin <alexander.shishkin@linux.intel.com>









S:	Supported
































drivers/net/wwan/Kconfig



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@@ -44,4 +44,16 @@ config MHI_WWAN_CTRL







	  To compile this driver as a module, choose M here: the module will be









	  called mhi_wwan_ctrl.



















config IOSM









	tristate "IOSM Driver for Intel M.2 WWAN Device"









	select WWAN_CORE









	depends on INTEL_IOMMU









	help









	  This driver enables Intel M.2 WWAN Device communication.



















	  If you have one of those Intel M.2 WWAN Modules and wish to use it in









	  Linux say Y/M here.



















	  If unsure, say N.



















endif # WWAN