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  1. 10 3月, 2020 33 次提交
  3. 09 3月, 2020 7 次提交
    • D
      Merge branch 'net-introduce-Qualcomm-IPA-driver' · fbd43602
      由 David S. Miller 提交于 
      Alex Elder says:

====================
net: introduce Qualcomm IPA driver (UPDATED)

This series presents the driver for the Qualcomm IP Accelerator (IPA).

This is version 2 of this updated series.  It includes the following
small changes since the previous version:
  - Now based on net-next instead of v5.6-rc
  - Config option now named CONFIG_QCOM_IPA
  - Some minor cleanup in the GSI code
  - Small change to replenish logic
  - No longer depends on remoteproc bug fixes
What follows is the basically same explanation as was posted previously.

					-Alex

I have posted earlier versions of this code previously, but it has
undergone quite a bit of development since the last time, so rather
than calling it "version 3" I'm just treating it as a new series
(indicating it's been updated in this message).  The fast/data path
is the same as before.  But the driver now (nearly) supports a
second platform, its transaction handling has been generalized
and improved, and modem activities are now handled in a more
unified way.

This series is available (based on net-next in branch "ipa_updated-v2"
in this git repository:
  https://git.linaro.org/people/alex.elder/linux.git

The branch depends on other one other small patch that I sent out
for review earlier.
  https://lore.kernel.org/lkml/20200306042302.17602-1-elder@linaro.org/

I want to address some of the discussion that arose last time.

First, there was the WWAN discussion.  Here's the history:
  - This was last posted nine months ago.
  - Reviewers at that time favored developing a new WWAN subsystem that
    would be used for managing devices like this.  And the suggestion
    was to not accept this driver until that could be developed.
  - Along the way, Apple acquired much of Intel's modem business.
    And as a result, the generic framework became less pressing.
  - I did participate in the WWAN subsystem design however, and
    although it went dormant for a while it's been resurrected:
      https://lore.kernel.org/netdev/20200225100053.16385-1-johannes@sipsolutions.net/
  - Unfortunately the proposed WWAN design was not an easy fit
    with Qualcomm's integrated modem interfaces.  Given that
    rmnet is a supported link type for in the upstream "iproute2"
    package (more on this below), I have opted not to integrate
    with any WWAN subsystem.

So in summary, this driver does not integrate with a generic WWAN
framework.  And I'd like it to be accepted upstream despite that.

Next, Arnd Bergmann had some concerns about flow control.  (Note:
some of my discussions with Arnd about this were offline.) The
overall architecture here also involves the "rmnet" driver:
  drivers/net/ethernet/qualcomm/rmnet

The rmnet driver presents a network device for use.  It connects
with another network device presented, by the IPA driver.  The
rmnet driver wraps (and unwraps) packets transferred to (and from)
the IPA driver with QMAP headers.

   ---------------
   | rmnet_data0 |    <-- "real" netdev
   ---------------
          ||       }- QMAP spoken here
   --------------
   | rmnet_ipa0 |     <-- also netdev, transporting QMAP packets
   --------------
          ||
   --------------
  ( IPA hardware )
   --------------

Arnd's concern was that the rmnet_data0 network device does not
have the benefit of information about the state of the underlying
IPA hardware in order to be effective in controlling TX flow.
The feared result is over-buffering of TX packets (bufferbloat).
I began working on some simple experiments to see whether (or how
much) his concern was warranted.  But it turned out that completing
these experiments was much more work than had been hoped.

The rmnet driver is present in the upstream kernel.  There is also
support for the rmnet link type in the upstream "ip" user space
command in the "iproute2" package.  Changing the layering of rmnet
over IPA likely involves deprecating the rmnet driver and its
support in "iproute2".  I would really rather not go down that
path.

There is precedent for this sort of layering of network devices
(L2TP, VLAN).  And any architecture like this would suffer the
issues Arnd mentioned; the problem is not limited to rmnet and IPA.
I do think this is a problem worth solving, but the prudent thing
to do might be to try to solve it more generally.

So to summarize on this issue, this driver does not attempt to
change the way the rmnet and IPA drivers work together.  And even
though I think Arnd's concerns warrant more investigation, I'd like
this driver to to be accepted upstream without any change to this
architecture.

Finally, a more technical description for the series, and some
acknowledgements to some people who contributed to it.

The IPA is a component present in some Qualcomm SoCs that allows
network functions such as aggregation, filtering, routing, and NAT
to be performed without active involvement of the main application
processor (AP).

In this initial patch series these advanced features are not
implemented.  The IPA driver simply provides a network interface
that makes the modem's LTE network available in Linux.  This initial
series supports only the Qualcomm SDM845 SoC.  The Qualcomm SC7180
SoC is partially supported, and support for other platforms will
follow.

This code is derived from a driver developed by Qualcomm.  A version
of the original source can be seen here:
  https://source.codeaurora.org/quic/la/kernel/msm-4.9/tree
in the "drivers/platform/msm/ipa" directory.  Many were involved in
developing this, but the following individuals deserve explicit
acknowledgement for their substantial contributions:

    Abhishek Choubey
    Ady Abraham
    Chaitanya Pratapa
    David Arinzon
    Ghanim Fodi
    Gidon Studinski
    Ravi Gummadidala
    Shihuan Liu
    Skylar Chang
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      fbd43602
    • A
      arm64: dts: sdm845: add IPA information · 9cc5ae12
      由 Alex Elder 提交于 
      Add IPA-related nodes and definitions to "sdm845.dtsi".
Signed-off-by: NAlex Elder <elder@linaro.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      9cc5ae12
    • A
      MAINTAINERS: add entry for the Qualcomm IPA driver · aa302745
      由 Alex Elder 提交于 
      Add an entry in the MAINTAINERS file for the Qualcomm IPA driver
Signed-off-by: NAlex Elder <elder@linaro.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      aa302745
    • A
      soc: qcom: ipa: support build of IPA code · 08120d23
      由 Alex Elder 提交于 
      Add build and Kconfig support for the Qualcomm IPA driver.
Signed-off-by: NAlex Elder <elder@linaro.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      08120d23
    • A
      soc: qcom: ipa: AP/modem communications · 530f9216
      由 Alex Elder 提交于 
      This patch implements two forms of out-of-band communication between
the AP and modem.

  - QMI is a mechanism that allows clients running on the AP
    interact with services running on the modem (and vice-versa).
    The AP IPA driver uses QMI to communicate with the corresponding
    IPA driver resident on the modem, to agree on parameters used
    with the IPA hardware and to ensure both sides are ready before
    entering operational mode.

  - SMP2P is a more primitive mechanism available for the modem and
    AP to communicate with each other.  It provides a means for either
    the AP or modem to interrupt the other, and furthermore, to provide
    32 bits worth of information.  The IPA driver uses SMP2P to tell
    the modem what the state of the IPA clock was in the event of a
    crash.  This allows the modem to safely access the IPA hardware
    (or avoid doing so) when a crash occurs, for example, to access
    information within the IPA hardware.
Signed-off-by: NAlex Elder <elder@linaro.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      530f9216
    • A
      soc: qcom: ipa: modem and microcontroller · a646d6ec
      由 Alex Elder 提交于 
      This patch includes code implementing the modem functionality.
There are several communication paths between the AP and modem,
separate from the main data path provided by IPA.  SMP2P provides
primitive messaging and interrupt capability, and QMI allows more
complex out-of-band messaging to occur between entities on the AP
and modem.  (SMP2P and QMI support are added by the next patch.)
Management of these (plus the network device implementing the data
path) is done by code within "ipa_modem.c".

Sort of unrelated, this patch also includes the code supporting the
microcontroller CPU present on the IPA.  The microcontroller can be
used to implement special handling of packets, but at this time we
don't support that.  Still, it is a component that needs to be
initialized, and in the event of a crash we need to do some
synchronization between the AP and the microcontroller.
Signed-off-by: NAlex Elder <elder@linaro.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      a646d6ec
    • A
      soc: qcom: ipa: immediate commands · 731c46ed
      由 Alex Elder 提交于 
      One TX endpoint (per EE) is used for issuing immediate commands to
the IPA.  These commands request activites beyond simple data
transfers to be done by the IPA hardware.  For example, the IPA is
able to manage routing packets among endpoints, and immediate commands
are used to configure tables used for that routing.

Immediate commands are built on top of GSI transactions.  They are
different from normal transfers (in that they use a special endpoint,
and their "payload" is interpreted differently), so separate functions
are used to issue immediate command transactions.
Signed-off-by: NAlex Elder <elder@linaro.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      731c46ed