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From:   Felipe Balbi <balbi@kernel.org>
To:     John Stultz <john.stultz@linaro.org>,
        lkml <linux-kernel@vger.kernel.org>
Cc:     John Stultz <john.stultz@linaro.org>,
        Felipe Balbi <felipe.balbi@linux.intel.com>,
        Yang Fei <fei.yang@intel.com>,
        Thinh Nguyen <thinhn@synopsys.com>,
        Tejas Joglekar <tejas.joglekar@synopsys.com>,
        Andrzej Pietrasiewicz <andrzej.p@collabora.com>,
        Jack Pham <jackp@codeaurora.org>, Todd Kjos <tkjos@google.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Linux USB List <linux-usb@vger.kernel.org>,
        stable <stable@vger.kernel.org>
Subject: Re: [RFC][PATCH 0/2] Avoiding DWC3 transfer stalls/hangs when using adb over f_fs
In-Reply-To: <20200122222645.38805-1-john.stultz@linaro.org>
References: <20200122222645.38805-1-john.stultz@linaro.org>
Date:   Thu, 23 Jan 2020 09:18:51 +0200
Message-ID: <87wo9i4p44.fsf@kernel.org>
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Hi,

John Stultz <john.stultz@linaro.org> writes:
> Hey all,
>   I wanted to send these out for comment and thoughts.
>
> Since ~4.20, when the functionfs gadget enabled scatter-gather
> support, we have seen problems with adb connections stalling and
> stopping to function on hardware with dwc3 usb controllers.
> Specifically, HiKey960, Dragonboard 845c, and Pixel3 devices.
>
> Initally the workaround we used was to simply disable scatter
> gather support on the dwc3 by commenting out the
> "dwc->gadget.sg_supported =3D true;" line.
>
> After working with Fei Yang, who was seeing similar trouble on
> Intel dwc3 based hardare, Thinh Nguyen mentioned that a fix had
> already been found and pointed me to one of Anurag's patches.
>
> This solved the issue on HiKey960 and I sent it out to the list
> but didn't get any feedback.
>
> Additional testing with the Dragonboard 845c found that that
> first fix was not sufficient, and so I've sat on the fix
> thinking something deeper was amiss and went back to the hack
> of disabling sg_supported on all dwc3 platforms.=20
>
> In the following months Fei's continued and repeated efforts
> didn't seem to get enough review to result in a fix, and they've
> since moved on to other work.
>
> Recently, I found that folks at qcom have seen similer issues
> and pointed me to the second patch in this series, which does
> seem to resolve the issue on the Dragonboard 845c, but not the
> HiKey960 on its own.
>
> So I wanted to send these patches out for comment. There's
> clearly a number of folks seeing broken behavior for ahwile on
> dwc3 hardware, and we're all seeemingly working around it in our
> own ways, so either those individual fixes need to get upstream
> or we need to figure out some deeper solution to the issue.
>
> So I wanted to send these two out for review and feedback.
>
> thanks
> -john
>
> Cc: Felipe Balbi <felipe.balbi@linux.intel.com>
> Cc: Yang Fei <fei.yang@intel.com>
> Cc: Thinh Nguyen <thinhn@synopsys.com>
> Cc: Tejas Joglekar <tejas.joglekar@synopsys.com>
> Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> Cc: Jack Pham <jackp@codeaurora.org>
> Cc: Todd Kjos <tkjos@google.com>
> Cc: Greg KH <gregkh@linuxfoundation.org>
> Cc: Linux USB List <linux-usb@vger.kernel.org>
> Cc: stable <stable@vger.kernel.org>
>
> Anurag Kumar Vulisha (2):
>   usb: dwc3: gadget: Check for IOC/LST bit in both event->status and
>     TRB->ctrl fields
>   usb: dwc3: gadget: Correct the logic for finding last SG entry

I remember commenting on these patches before and never getting a newer
version from Anurag.

=2D-=20
balbi

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