linux-kernel - Re: [PATCH v3] usb: dwc3: Issue core soft reset before enabling run/stop

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Date:   Tue, 15 Mar 2022 18:10:58 -0700
From:   Wesley Cheng <wcheng@...eaurora.org>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Wesley Cheng <quic_wcheng@...cinc.com>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Cc:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>
Subject: Re: [PATCH v3] usb: dwc3: Issue core soft reset before enabling
 run/stop



On 3/15/2022 5:28 PM, Thinh Nguyen wrote:
> 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>
>> ---
>>  Changes in v3:
>>    - Removed change from RFC series and placed into its own patch.
>>
>>  Previous patches:
>>   https://urldefense.com/v3/__https://lore.kernel.org/linux-usb/20220203080017.27339-1-quic_wcheng@quicinc.com/__;!!A4F2R9G_pg!OjNviLgYSUvXpUWpeTDiI6OVuwjW2kjQpACAYYo5MdI09GClnUHLGFjuoMrtquF8Qe9X$ 
>>
>>  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 eb9c1efced05..86e27afef6c5 100644
>> --- a/drivers/usb/dwc3/core.h
>> +++ b/drivers/usb/dwc3/core.h
>> @@ -1530,6 +1530,8 @@ 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 a0c883f19a41..448ff6cb9c22 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -2544,6 +2544,17 @@ 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
Hi Thinh,

Thanks for the review.
> 
> It's "Synopsys". Version 1.90a is for DWC_usb31 controller.
> 
Ah, I need to get the incorrect spelling out of my head! :)

>> +		 * 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.
> 
> Just want to note that we're skipping some controller initialization on
> soft-reset here. But it's probably fine because the global registers
> don't get reset on soft reset. Just need to make sure that the registers
> that do get reset get reinitialized on __dwc3_gadget_start().
> 
>> +		 */
>> +		spin_unlock_irqrestore(&dwc->lock, flags);
>> +		dwc3_core_soft_reset(dwc);
>> +		spin_lock_irqsave(&dwc->lock, flags);
>> +
>> +		dwc3_event_buffers_setup(dwc);
>>  		__dwc3_gadget_start(dwc);
>>  	}
>>  
> 
> It's a little awkward because dwc3 also issues soft-reset during driver
> probe. Pullup() is called during driver bindings. So soft-reset is
> called multiple times. I don't have a better solution at the moment, but
> I don't see a problem with it either.
> Correct...this would mainly help w/ the soft connect/disconnect
situations.  Will fixup the typos and resend.

> After fixing the typos,
> 
> Reviewed-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
> 
> Thanks,
> Thinh

Thanks
Wesley Cheng

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