linux-kernel - Re: [PATCH v2 1/2] usb: dwc3: gadget: Bail out in pullup if soft reset timeout happens

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Date:   Thu, 30 Mar 2023 00:10:11 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>
CC:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Colin Ian King <colin.i.king@...il.com>,
        Jiantao Zhang <water.zhangjiantao@...wei.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "quic_ppratap@...cinc.com" <quic_ppratap@...cinc.com>,
        "quic_wcheng@...cinc.com" <quic_wcheng@...cinc.com>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>,
        "quic_ugoswami@...cinc.com" <quic_ugoswami@...cinc.com>
Subject: Re: [PATCH v2 1/2] usb: dwc3: gadget: Bail out in pullup if soft
 reset timeout happens

On Wed, Mar 29, 2023, Krishna Kurapati PSSNV wrote:
> 
> 
> On 3/29/2023 2:50 AM, Thinh Nguyen wrote:
> > Hi,
> > 
> > On Tue, Mar 28, 2023, Krishna Kurapati wrote:
> > > If the core soft reset timeout happens, avoid setting up event
> > > buffers and starting gadget as the writes to these registers
> > > may not reflect when in reset and setting the run stop bit
> > > can lead the controller to access wrong event buffer address
> > > resulting in a crash.
> > > 
> > > Signed-off-by: Krishna Kurapati <quic_kriskura@...cinc.com>
> > > ---
> > >   drivers/usb/dwc3/gadget.c | 5 ++++-
> > >   1 file changed, 4 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> > > index 3c63fa97a680..f0472801d9a5 100644
> > > --- a/drivers/usb/dwc3/gadget.c
> > > +++ b/drivers/usb/dwc3/gadget.c
> > > @@ -2620,13 +2620,16 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
> > >   		 * device-initiated disconnect requires a core soft reset
> > >   		 * (DCTL.CSftRst) before enabling the run/stop bit.
> > >   		 */
> > > -		dwc3_core_soft_reset(dwc);
> > > +		ret = dwc3_core_soft_reset(dwc);
> > > +		if (ret)
> > > +			goto done;
> > >   		dwc3_event_buffers_setup(dwc);
> > >   		__dwc3_gadget_start(dwc);
> > >   		ret = dwc3_gadget_run_stop(dwc, true, false);
> > >   	}
> > > +done:
> > >   	pm_runtime_put(dwc->dev);
> > >   	return ret;
> > > -- 
> > > 2.40.0
> > > 
> > 
> > I think there's one more place that may needs this check. Can you also
> > add this check in __dwc3_set_mode()?
> 
> Hi Thinh,
> 
>   Sure. Will do it.
> Will the below be good enough ? Or would it be good to add an error/warn log
> there>

There's already a warning message in dwc3_core_soft_reset() if it fails.

> 
> kriskura@...kriskura-hyd:/local/mnt/workspace/krishna/skales2/skales/kernel$
> git diff drivers/usb/
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 476b63618511..8d1d213d1dcd 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -210,7 +210,9 @@ static void __dwc3_set_mode(struct work_struct *work)
>                 }
>                 break;
>         case DWC3_GCTL_PRTCAP_DEVICE:
> -               dwc3_core_soft_reset(dwc);
> +               ret = dwc3_core_soft_reset(dwc);
> +               if (ret)
> +                       goto out;
> 
>                 dwc3_event_buffers_setup(dwc);
> 

If soft-reset failed, the controller is in a bad state. We should not
perform any further operation until the next hard reset. We should flag
the controller as dead. I don't think we have the equivalent of the
host's HCD_FLAG_DEAD. It may require some work in the UDC core. Perhaps
we can flag within dwc3 for now and prevent any further operation for a
simpler fix.

Thanks,
Thinh