linux-kernel - Re: [PATCH v5 0/3] Avoid having pending end transfers on soft disconnect

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Message-ID: <ZEEEIfqTKiM6CKAR@kroah.com>
Date:   Thu, 20 Apr 2023 11:21:37 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Wesley Cheng <quic_wcheng@...cinc.com>
Cc:     Thinh.Nguyen@...opsys.com, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH v5 0/3] Avoid having pending end transfers on soft
 disconnect

On Thu, Apr 13, 2023 at 12:57:39PM -0700, Wesley Cheng wrote:
> In case there is a host which takes time to complete a SETUP transaction,
> during the soft disconnect sequence multiple DWC3 EPs will have their
> DWC3_EP_DELAY_STOP flag set w/o issuing the end transfer command.  Once the
> controller halt sequence occurs, the soft disconnect is successful, and
> the subsequent soft connect will attempt to flush the pending end transfers.
> 
> Soft disconnect sequence:
>   dwc3_gadget_ep_disable   name=ep8in flags=0x3009  direction=1
>   dwc3_gadget_ep_disable   name=ep4in flags=1  direction=1
>   dwc3_gadget_ep_disable   name=ep3out flags=1  direction=0
>   usb_gadget_disconnect   deactivated=0  connected=0  ret=0
> 
> Soft connect bug:
>   BUG: spinlock already unlocked on CPU
>   spin_bug+0x0
>   dwc3_remove_requests+0x278
>   dwc3_ep0_out_start+0xb0
>   __dwc3_gadget_start+0x25c
> 
> The bug occurs due to the flush of the pending end transfers, as the gadget
> start routine is not held with a spinlock.  However, if the DWC3_EP_DELAY_STOP
> is set, it will call the giveback API, which attempts to unlock the dwc->lock.
> Ideally, the DWC3 gadget should not have pending end transfers on a soft
> connect, so fix this by:
> 
>  1. Re-locating the SETUP phase check after stop active transfers, since
>  that is where the DWC3_EP_DELAY_STOP is potentially set.  This also allows
>  for handling of a host that may be unresponsive by using the completion
>  timeout to trigger the stall and restart for EP0.
> 
>  2. Do not call gadget stop until the poll for controller halt is
>  completed.  DEVTEN is cleared as part of gadget stop, so the intention to
>  allow ep0 events to continue while waiting for controller halt is not
>  happening.

Only patch 1 applied, can you rebase the rest and resend with the acks
applied?

thanks,

greg k-h