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Date:   Mon, 31 May 2021 16:49:56 +0200
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     Thinh Nguyen <Thinh.Nguyen@synopsys.com>,
        Felipe Balbi <balbi@kernel.org>,
        USB <linux-usb@vger.kernel.org>, Ferry Toth <fntoth@gmail.com>,
        Wesley Cheng <wcheng@codeaurora.org>
Subject: Re: v5.13-rc3 --> v5.13-rc4 DWC3 breakage
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On Mon, May 31, 2021 at 05:33:02PM +0300, Andy Shevchenko wrote:
> Hi!
> 
> The only patch that made v5.13-rc4 effectively broke USB on Intel Merrifield.
> 
> My reproducer:
>  1. Boot with switch in gadget mode
>  2. Enable USB ethernet
>  3. Switch to host
>  4. wait a bit for device enumeration, etc
>  5. Switch back
>  6. No gadget mode, kernel RCU stall detected (USB become unusable, so
> does the system)
> 
> [  115.792620] rcu: INFO: rcu_sched self-detected stall on CPU
> [  115.798410] rcu:     0-....: (24089 ticks this GP)
> idle=886/1/0x4000000000000000 softirq=3796/3797 fqs=5240
> [  115.808333]  (t=21000 jiffies g=6505 q=12158)
> [  115.812847] NMI backtrace for cpu 0
> [  115.816472] CPU: 0 PID: 23 Comm: kworker/0:1 Not tainted 5.13.0-rc4+ #213
> ...
> 
> [  115.977913]  add_dma_entry+0xd4/0x1d0
> [  115.981760]  dma_map_page_attrs+0xd8/0x220
> [  115.986063]  usb_hcd_map_urb_for_dma+0x3b6/0x4f0
> [  115.990895]  usb_hcd_submit_urb+0x98/0xbf0
> [  115.995263]  dln2_rx+0x1ae/0x280 [dln2]
> ...
> 
> 100% Reproducibility, revert of the 25dda9fc56bd ("usb: dwc3: gadget:
> Properly track pending and queued SG") fixes the issue.
> 
> Please, fix it properly or revert. Thanks!

Care to send the revert?

thanks,

greg k-h