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[v2,0/3] Re-introduce TX FIFO resize for larger EP bursting

Message ID 1590050169-30747-1-git-send-email-wcheng@codeaurora.org (mailing list archive)
Headers show
Series Re-introduce TX FIFO resize for larger EP bursting | expand

Message

Wesley Cheng May 21, 2020, 8:36 a.m. UTC
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 <balbi@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>

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(-)

Comments

Wesley Cheng May 21, 2020, 5:37 p.m. UTC | #1
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 <balbi@kernel.org>
> Reviewed-by: Rob Herring <robh@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(-)
>
Felipe Balbi May 22, 2020, 9:54 a.m. UTC | #2
Wesley Cheng <wcheng@codeaurora.org> writes:

> 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 <balbi@kernel.org>

I don't remember giving you a Reviewed-by, did I?
Wesley Cheng May 22, 2020, 5:49 p.m. UTC | #3
On 5/22/2020 2:54 AM, Felipe Balbi wrote:
> Wesley Cheng <wcheng@codeaurora.org> writes:
> 
>> 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 <balbi@kernel.org>
> 
> I don't remember giving you a Reviewed-by, did I?
> 

Hi Felipe,

Sorry, I put the Reviewed-by tag by mistake, I sent a follow up email to
disregard the tags.  If you need me to resubmit the patch series
version, please let me know.  Thanks!