[lkml]   [2020]   [May]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC v3 0/3] Re-introduce TX FIFO resize for larger EP bursting
On Wed, May 27, 2020 at 06:46:00PM -0700, Wesley Cheng wrote:
> Changes in V3:
> - Removed "Reviewed-by" tags
> - Renamed series back to RFC
> - Modified logic to ensure that fifo_size is reset if we pass the minimum
> threshold. Tested with binding multiple FDs requesting 6 FIFOs.
> Changes in V2:
> - Modified TXFIFO resizing logic to ensure that each EP is reserved a
> - Removed dev_dbg() prints and fixed typos from patches
> - Added some more description on the dt-bindings commit message
> 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.

Why is this still a "RFC" series? That implies you don't want this

 \ /
  Last update: 2020-05-29 12:13    [W:0.111 / U:1.076 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site