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From:   John Stultz <john.stultz@linaro.org>
Date:   Fri, 24 Apr 2020 13:01:35 -0700
Message-ID: <CALAqxLUSr8vnW3MgK+GZk80c8D58PXM6ovN66y0hwFbURrBpiA@mail.gmail.com>
Subject: Re: More dwc3 gadget issues with adb
To:     Jack Pham <jackp@codeaurora.org>
Cc:     Felipe Balbi <balbi@kernel.org>, Josh Gao <jmgao@google.com>,
        YongQin Liu <yongqin.liu@linaro.org>,
        Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>,
        Yang Fei <fei.yang@intel.com>,
        Thinh Nguyen <thinhn@synopsys.com>,
        Tejas Joglekar <tejas.joglekar@synopsys.com>,
        Andrzej Pietrasiewicz <andrzej.p@collabora.com>,
        Todd Kjos <tkjos@google.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Linux USB List <linux-usb@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>
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On Fri, Apr 24, 2020 at 11:36 AM John Stultz <john.stultz@linaro.org> wrote:
> On Fri, Apr 24, 2020 at 10:12 AM Jack Pham <jackp@codeaurora.org> wrote:
> > On Tue, Apr 21, 2020 at 10:09:27PM -0700, John Stultz wrote:
> > > Does something like this make sense? It's not causing trouble on
> > > db845c either so far in my testing.
> >
> > Ok I'll bite...
> >
> > I'm now curious why it hasn't been a problem with the Qualcomm HW. Do
> > you mind please capturing a similar trace log on the db845c?  Would be
> > good to see a side-by-side comparison and see if, first of all, whether
> > the same S/G path is getting exercised (i.e. 16KiB OUT requests from ADB
> > userspace using AIO which then get broken up into 4K chunks by f_fs),
> > and what the behaviors of the reclaim_trb and giveback are when the
> > transfer is completed.
> >
> > Preferably if you could get a trace without your patch applied that
> > would be great. And maybe also one after your patch just to see if the
> > traces are truly identical or not.
>
> Sure. I've captured logs in the same manner with and without on db845c
> (against 5.7-rc2). See attached.
>
> I suspect the difference is the db845c is using an iommu (I don't
> think it will boot without it) where hikey960 isn't, but I'll let you
> take a look.

And I've added my own printk debugging that I used to track the issue
down on HiKey960 and on the db845c we are never hitting the case where
the HWO flag is set when we call dwc3_gadget_ep_reclaim_trb_sg()

thanks
-john