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    Subject[RFC PATCH net-next 0/4] net: wwan: Add Qualcomm BAM-DMUX WWAN network driver
    Date
    The BAM Data Multiplexer provides access to the network data channels
    of modems integrated into many older Qualcomm SoCs, e.g. Qualcomm MSM8916
    or MSM8974. This series adds a driver that allows using it.

    For more information about BAM-DMUX, see PATCH 4/4.

    Shortly said, BAM-DMUX is built using a simple protocol layer on top of
    a DMA engine (Qualcomm BAM DMA). For BAM-DMUX, the BAM DMA engine runs in
    a quite strange mode that I call "remote power collapse", where the
    modem/remote side is responsible for powering on the BAM when needed but we
    are responsible to initialize it. The BAM is power-collapsed when unneeded
    by coordinating power control via bidirectional interrupts from the
    BAM-DMUX driver.

    The series first adds one possible solution for handling this "remote power
    collapse" mode in the bam_dma driver, then it adds the BAM-DMUX driver to
    the WWAN subsystem. Note that the BAM-DMUX driver does not actually make
    use of the WWAN subsystem yet, since I'm not sure how to fit it in there
    yet (see PATCH 4/4).

    Please note that all of the changes in this patch series are based on
    a fairly complicated driver from Qualcomm [1].
    I do not have access to any documentation about "BAM-DMUX". :(

    The driver has been used in postmarketOS [2] on various smartphones/tablets
    based on Qualcomm MSM8916 and MSM8974 for a year now with no reported
    problems.

    At runtime (but not compile-time), the following two patches are needed
    additionally for full functionality:
    - https://lore.kernel.org/linux-arm-msm/20210712135703.324748-1-stephan@gerhold.net/
    - https://lore.kernel.org/linux-arm-msm/20210712135703.324748-2-stephan@gerhold.net/

    [1]: https://source.codeaurora.org/quic/la/kernel/msm-3.10/tree/drivers/soc/qcom/bam_dmux.c?h=LA.BR.1.2.9.1-02310-8x16.0
    [2]: https://postmarketos.org/

    Stephan Gerhold (4):
    dt-bindings: dmaengine: bam_dma: Add remote power collapse mode
    dmaengine: qcom: bam_dma: Add remote power collapse mode
    dt-bindings: net: Add schema for Qualcomm BAM-DMUX
    net: wwan: Add Qualcomm BAM-DMUX WWAN network driver

    .../devicetree/bindings/dma/qcom_bam_dma.txt | 2 +
    .../bindings/net/qcom,bam-dmux.yaml | 87 ++
    MAINTAINERS | 8 +
    drivers/dma/qcom/bam_dma.c | 88 +-
    drivers/net/wwan/Kconfig | 13 +
    drivers/net/wwan/Makefile | 1 +
    drivers/net/wwan/qcom_bam_dmux.c | 907 ++++++++++++++++++
    7 files changed, 1074 insertions(+), 32 deletions(-)
    create mode 100644 Documentation/devicetree/bindings/net/qcom,bam-dmux.yaml
    create mode 100644 drivers/net/wwan/qcom_bam_dmux.c

    --
    2.32.0

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