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SubjectRe: [PATCH v2] usb: dwc3: gadget: Check for IOC/LST bit in TRB->ctrl fields


John Stultz <> writes:
> From: Anurag Kumar Vulisha <>
> The current code in dwc3_gadget_ep_reclaim_completed_trb() will
> check for IOC/LST bit in the event->status and returns if
> IOC/LST bit is set. This logic doesn't work if multiple TRBs
> are queued per request and the IOC/LST bit is set on the last
> TRB of that request.
> Consider an example where a queued request has multiple queued
> TRBs and IOC/LST bit is set only for the last TRB. In this case,
> the core generates XferComplete/XferInProgress events only for
> the last TRB (since IOC/LST are set only for the last TRB). As
> per the logic in dwc3_gadget_ep_reclaim_completed_trb()
> event->status is checked for IOC/LST bit and returns on the
> first TRB. This leaves the remaining TRBs left unhandled.
> Similarly, if the gadget function enqueues an unaligned request
> with sglist already in it, it should fail the same way, since we
> will append another TRB to something that already uses more than
> one TRB.
> To aviod this, this patch changes the code to check for IOC/LST
> bits in TRB->ctrl instead.
> At a practical level, this patch resolves USB transfer stalls seen
> with adb on dwc3 based HiKey960 after functionfs gadget added
> scatter-gather support around v4.20.
> Cc: Felipe Balbi <>
> Cc: Yang Fei <>
> Cc: Thinh Nguyen <>
> Cc: Tejas Joglekar <>
> Cc: Andrzej Pietrasiewicz <>
> Cc: Jack Pham <>
> Cc: Todd Kjos <>
> Cc: Greg KH <>
> Cc: Linux USB List <>
> Cc: stable <>
> Tested-by: Tejas Joglekar <>
> Reviewed-by: Thinh Nguyen <>
> Signed-off-by: Anurag Kumar Vulisha <>
> [jstultz: forward ported to mainline, reworded commit log, reworked
> to only check trb->ctrl as suggested by Felipe]
> Signed-off-by: John Stultz <>

since v5.5 is already merged, I'll send this to Greg once -rc1 is
tagged. It's already in my testing/fixes branch waiting for a pull


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