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    Subject[RFC 0/3] Re-introduce TX FIFO resize for larger EP bursting
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    Currently, there is no functionality to allow for resizing the TXFIFOs, and
    relying on the HW default setting for the TXFIFO depth. In most cases, the
    HW default is probably sufficient, but for USB compositions that contain
    multiple functions that require EP bursting, the default settings
    might not be enough. Also to note, the current SW will assign an EP to a
    function driver w/o checking to see if the TXFIFO size for that particular
    EP is large enough. (this is a problem if there are multiple HW defined
    values for the TXFIFO size)

    It is mentioned in the SNPS databook that a minimum of TX FIFO depth = 3
    is required for an EP that supports bursting. Otherwise, there may be
    frequent occurences of bursts ending. For high bandwidth functions,
    such as data tethering (protocols that support data aggregation), mass
    storage, and media transfer protocol (over FFS), the bMaxBurst value can be
    large, and a bigger TXFIFO depth may prove to be beneficial in terms of USB
    throughput. (which can be associated to system access latency, etc...) It
    allows for a more consistent burst of traffic, w/o any interruptions, as
    data is readily available in the FIFO.

    With testing done using the mass storage function driver, the results show
    that with a larger TXFIFO depth, the bandwidth increased significantly.

    Test Parameters:
    - Platform: Qualcomm SM8150
    - bMaxBurst = 6
    - USB req size = 256kB
    - Num of USB reqs = 16
    - USB Speed = Super-Speed
    - Function Driver: Mass Storage (w/ ramdisk)
    - Test Application: CrystalDiskMark

    Results:

    TXFIFO Depth = 3 max packets

    Test Case | Data Size | AVG tput (in MB/s)
    -------------------------------------------
    Sequential|1 GB x |
    Read |9 loops | 193.60
    | | 195.86
    | | 184.77
    | | 193.60
    -------------------------------------------

    TXFIFO Depth = 6 max packets

    Test Case | Data Size | AVG tput (in MB/s)
    -------------------------------------------
    Sequential|1 GB x |
    Read |9 loops | 287.35
    | | 304.94
    | | 289.64
    | | 293.61
    -------------------------------------------

    Wesley Cheng (3):
    usb: dwc3: Resize TX FIFOs to meet EP bursting requirements
    arm64: boot: dts: qcom: sm8150: Enable dynamic TX FIFO resize logic
    dt-bindings: usb: dwc3: Add entry for tx-fifo-resize

    Documentation/devicetree/bindings/usb/dwc3.txt | 2 +-
    arch/arm64/boot/dts/qcom/sm8150.dtsi | 1 +
    drivers/usb/dwc3/core.c | 2 +
    drivers/usb/dwc3/core.h | 6 ++
    drivers/usb/dwc3/ep0.c | 40 ++++++++++-
    drivers/usb/dwc3/gadget.c | 95 ++++++++++++++++++++++++++
    6 files changed, 144 insertions(+), 2 deletions(-)

    --
    The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
    a Linux Foundation Collaborative Project

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