On 5/21/2020 1:36 AM, Wesley Cheng wrote:
> Changes in V2:
> - Modified TXFIFO resizing logic to ensure that each EP is reserved a
> FIFO.
> - Removed dev_dbg() prints and fixed typos from patches
> - Added some more description on the dt-bindings commit message
>
> Reviewed-by: Felipe Balbi <ba...@kernel.org>
> Reviewed-by: Rob Herring <r...@kernel.org>
>
Sorry, please disregard the Reviewed-by tags in the patches. I added
those mistakenly.
> 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 | 8 ++
> drivers/usb/dwc3/ep0.c | 37 ++++++++-
> drivers/usb/dwc3/gadget.c | 111
> +++++++++++++++++++++++++
> 6 files changed, 159 insertions(+), 2 deletions(-)
>
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