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 14:52:14 +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

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

>  		__dwc3_gadget_start(dwc);
>  	}
>  
>