[PATCH v3 00/25] Add initial support for MHI endpoint stack

Manivannan Sadhasivam
2022-02-12T18:21:46Z

Hello,

This series adds initial support for the Qualcomm specific Modem Host Interface
(MHI) bus in endpoint devices like SDX55 modems. The MHI bus in endpoint devices
communicates with the MHI bus in host machines like x86 over any physical bus
like PCIe. The MHI host support is already in mainline [1] and been used by PCIe
based modems and WLAN devices running vendor code (downstream).

Overview
========

This series aims at adding the MHI support in the endpoint devices with the goal
of getting data connectivity using the mainline kernel running on the modems.
Modems here refer to the combination of an APPS processor (Cortex A grade) and
a baseband processor (DSP). The MHI bus is located in the APPS processor and it
transfers data packets from the baseband processor to the host machine.

The MHI Endpoint (MHI EP) stack proposed here is inspired by the downstream
code written by Qualcomm. But the complete stack is mostly re-written to adapt
to the "bus" framework and made it modular so that it can work with the upstream
subsystems like "PCI Endpoint". The code structure of the MHI endpoint stack
follows the MHI host stack to maintain uniformity.

With this initial MHI EP stack (along with few other drivers), we can establish
the network interface between host and endpoint over the MHI software channels
(IP_SW0) and can do things like IP forwarding, SSH, etc...

Stack Organization
==================

The MHI EP stack has the concept of controller and device drivers as like the
MHI host stack. The MHI EP controller driver can be a PCI Endpoint Function
driver and the MHI device driver can be a MHI EP Networking driver or QRTR
driver. The MHI EP controller driver is tied to the PCI Endpoint subsystem and
handles all bus related activities like mapping the host memory, raising IRQ,
passing link specific events etc... The MHI EP networking driver is tied to the
Networking stack and handles all networking related activities like
sending/receiving the SKBs from netdev, statistics collection etc...

This series only contains the MHI EP code, whereas the PCIe EPF driver and MHI
EP Networking drivers are not yet submitted and can be found here [2]. Though
the MHI EP stack doesn't have the build time dependency, it cannot function
without them.

Test setup
==========

This series has been tested on Telit FN980 TLB board powered by Qualcomm SDX55
(a.k.a X55 modem) and Qualcomm SM8450 based dev board.

For testing the stability and performance, networking tools such as iperf, ssh
and ping are used.

Limitations
===========

We are not _yet_ there to get the data packets from the modem as that involves
the Qualcomm IP Accelerator (IPA) integration with MHI endpoint stack. But we
are planning to add support for it in the coming days.

References
==========

MHI bus: https://www.kernel.org/doc/html/latest/mhi/mhi.html
Linaro connect presentation around this topic: https://connect.linaro.org/resources/lvc21f/lvc21f-222/

Thanks,
Mani

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/bus/mhi
[2] https://git.linaro.org/landing-teams/working/qualcomm/kernel.git/log/?h=tracking-qcomlt-sdx55-drivers

Changes in v3:

* Splitted the patch 20/23 into two.
* Fixed the error handling in patch 21/23.
* Removed spurious change in patch 01/23.
* Added check for xfer callbacks in client driver probe.

Changes in v2:

v2 mostly addresses the issues seen while testing the stack on SM8450 that is a
SMP platform and also incorporates the review comments from Alex.

Major changes are:

* Added a cleanup patch for getting rid of SHIFT macros and used the bitfield
operations.
* Added the endianess patches that were submitted to MHI list and used the
endianess conversion in EP patches also.
* Added support for multiple event rings.
* Fixed the MSI generation based on the event ring index.
* Fixed the doorbell list handling by making use of list splice and not locking
the entire list manipulation.
* Added new APIs for wrapping the reading and writing to host memory (Dmitry).
* Optimized the read_channel and queue_skb function logics.
* Added Hemant's R-o-b tag.

Manivannan Sadhasivam (23):
bus: mhi: Move host MHI code to "host" directory
bus: mhi: Move common MHI definitions out of host directory
bus: mhi: Make mhi_state_str[] array static inline and move to
common.h
bus: mhi: Cleanup the register definitions used in headers
bus: mhi: Get rid of SHIFT macros and use bitfield operations
bus: mhi: ep: Add support for registering MHI endpoint controllers
bus: mhi: ep: Add support for registering MHI endpoint client drivers
bus: mhi: ep: Add support for creating and destroying MHI EP devices
bus: mhi: ep: Add support for managing MMIO registers
bus: mhi: ep: Add support for ring management
bus: mhi: ep: Add support for sending events to the host
bus: mhi: ep: Add support for managing MHI state machine
bus: mhi: ep: Add support for processing MHI endpoint interrupts
bus: mhi: ep: Add support for powering up the MHI endpoint stack
bus: mhi: ep: Add support for powering down the MHI endpoint stack
bus: mhi: ep: Add support for handling MHI_RESET
bus: mhi: ep: Add support for handling SYS_ERR condition
bus: mhi: ep: Add support for processing command ring
bus: mhi: ep: Add support for reading from the host
bus: mhi: ep: Add support for processing transfer ring
bus: mhi: ep: Add support for queueing SKBs to the host
bus: mhi: ep: Add support for suspending and resuming channels
bus: mhi: ep: Add uevent support for module autoloading

Paul Davey (2):
bus: mhi: Fix pm_state conversion to string
bus: mhi: Fix MHI DMA structure endianness

drivers/bus/Makefile | 2 +-
drivers/bus/mhi/Kconfig | 28 +-
drivers/bus/mhi/Makefile | 9 +-
drivers/bus/mhi/common.h | 319 ++++
drivers/bus/mhi/ep/Kconfig | 10 +
drivers/bus/mhi/ep/Makefile | 2 +
drivers/bus/mhi/ep/internal.h | 254 ++++
drivers/bus/mhi/ep/main.c | 1601 +++++++++++++++++++++
drivers/bus/mhi/ep/mmio.c | 274 ++++
drivers/bus/mhi/ep/ring.c | 267 ++++
drivers/bus/mhi/ep/sm.c | 174 +++
drivers/bus/mhi/host/Kconfig | 31 +
drivers/bus/mhi/{core => host}/Makefile | 4 +-
drivers/bus/mhi/{core => host}/boot.c | 17 +-
drivers/bus/mhi/{core => host}/debugfs.c | 40 +-
drivers/bus/mhi/{core => host}/init.c | 123 +-
drivers/bus/mhi/{core => host}/internal.h | 427 +-----
drivers/bus/mhi/{core => host}/main.c | 46 +-
drivers/bus/mhi/{ => host}/pci_generic.c | 0
drivers/bus/mhi/{core => host}/pm.c | 36 +-
include/linux/mhi_ep.h | 293 ++++
include/linux/mod_devicetable.h | 2 +
scripts/mod/file2alias.c | 10 +
23 files changed, 3442 insertions(+), 527 deletions(-)
create mode 100644 drivers/bus/mhi/common.h
create mode 100644 drivers/bus/mhi/ep/Kconfig
create mode 100644 drivers/bus/mhi/ep/Makefile
create mode 100644 drivers/bus/mhi/ep/internal.h
create mode 100644 drivers/bus/mhi/ep/main.c
create mode 100644 drivers/bus/mhi/ep/mmio.c
create mode 100644 drivers/bus/mhi/ep/ring.c
create mode 100644 drivers/bus/mhi/ep/sm.c
create mode 100644 drivers/bus/mhi/host/Kconfig
rename drivers/bus/mhi/{core => host}/Makefile (54%)
rename drivers/bus/mhi/{core => host}/boot.c (96%)
rename drivers/bus/mhi/{core => host}/debugfs.c (90%)
rename drivers/bus/mhi/{core => host}/init.c (93%)
rename drivers/bus/mhi/{core => host}/internal.h (50%)
rename drivers/bus/mhi/{core => host}/main.c (98%)
rename drivers/bus/mhi/{ => host}/pci_generic.c (100%)
rename drivers/bus/mhi/{core => host}/pm.c (97%)
create mode 100644 include/linux/mhi_ep.h

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2.25.1