linux-kernel - Re: [RFC PATCH v2 3/3] usb: dwc3: Issue core soft reset before enabling run/stop

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Date:   Thu, 17 Feb 2022 18:43:54 +0900
From:   Jung Daehwan <dh10.jung@...sung.com>
To:     Wesley Cheng <quic_wcheng@...cinc.com>
Cc:     balbi@...nel.org, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_jackp@...cinc.com, Thinh.Nguyen@...opsys.com
Subject: Re: [RFC PATCH v2 3/3] usb: dwc3: Issue core soft reset before
 enabling run/stop

On Thu, Feb 17, 2022 at 02:52:14PM +0900, Jung Daehwan wrote:
> Hi wesley,
> 
> On Tue, Feb 15, 2022 at 04:08:35PM -0800, Wesley Cheng wrote:
> > It is recommended by the Synopsis databook to issue a DCTL.CSftReset
> > when reconnecting from a device-initiated disconnect routine.  This
> > resolves issues with enumeration during fast composition switching
> > cases, which result in an unknown device on the host.
> > 
> > Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.com>
> > ---
> >  drivers/usb/dwc3/core.c   |  4 +---
> >  drivers/usb/dwc3/core.h   |  2 ++
> >  drivers/usb/dwc3/gadget.c | 11 +++++++++++
> >  3 files changed, 14 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > index 18adddfba3da..02d10e1cb774 100644
> > --- a/drivers/usb/dwc3/core.c
> > +++ b/drivers/usb/dwc3/core.c
> > @@ -115,8 +115,6 @@ void dwc3_set_prtcap(struct dwc3 *dwc, u32 mode)
> >  	dwc->current_dr_role = mode;
> >  }
> >  
> > -static int dwc3_core_soft_reset(struct dwc3 *dwc);
> > -
> >  static void __dwc3_set_mode(struct work_struct *work)
> >  {
> >  	struct dwc3 *dwc = work_to_dwc(work);
> > @@ -261,7 +259,7 @@ u32 dwc3_core_fifo_space(struct dwc3_ep *dep, u8 type)
> >   * dwc3_core_soft_reset - Issues core soft reset and PHY reset
> >   * @dwc: pointer to our context structure
> >   */
> > -static int dwc3_core_soft_reset(struct dwc3 *dwc)
> > +int dwc3_core_soft_reset(struct dwc3 *dwc)
> >  {
> >  	u32		reg;
> >  	int		retries = 1000;
> > diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> > index 00348d6d479b..b27ad8dad317 100644
> > --- a/drivers/usb/dwc3/core.h
> > +++ b/drivers/usb/dwc3/core.h
> > @@ -1532,6 +1532,8 @@ bool dwc3_has_imod(struct dwc3 *dwc);
> >  int dwc3_event_buffers_setup(struct dwc3 *dwc);
> >  void dwc3_event_buffers_cleanup(struct dwc3 *dwc);
> >  
> > +int dwc3_core_soft_reset(struct dwc3 *dwc);
> > +
> >  #if IS_ENABLED(CONFIG_USB_DWC3_HOST) || IS_ENABLED(CONFIG_USB_DWC3_DUAL_ROLE)
> >  int dwc3_host_init(struct dwc3 *dwc);
> >  void dwc3_host_exit(struct dwc3 *dwc);
> > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> > index 0c89baedf220..788889f924f9 100644
> > --- a/drivers/usb/dwc3/gadget.c
> > +++ b/drivers/usb/dwc3/gadget.c
> > @@ -2585,6 +2585,17 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
> >  						dwc->ev_buf->length;
> >  		}
> >  	} else {
> > +		/*
> > +		 * In the Synopsis DesignWare Cores USB3 Databook Rev. 1.90a
> > +		 * Section 4.1.9, it specifies that for a reconnect after a
> > +		 * device-initiated disconnect requires a core soft reset
> > +		 * (DCTL.CSftRst) before enabling the run/stop bit.
> > +		 */
> > +		spin_unlock_irqrestore(&dwc->lock, flags);
> > +		dwc3_core_soft_reset(dwc);
> > +		spin_lock_irqsave(&dwc->lock, flags);
> > +
> > +		dwc3_event_buffers_setup(dwc);
> 
> Could you tell me why you add dwc3_event_buffer_setup?
> 
> Best Regards,
> Jung Daehwan
> 

I'm sorry I misunderstood databook then. It seems to be needed.

Best Regrards,
Jung Daehwan

> >  		__dwc3_gadget_start(dwc);
> >  	}
> >  
> >