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

Wesley Cheng
2022-03-16T01:11:10Z

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@quicinc.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@synopsys.com>
>
> Thanks,
> Thinh

Thanks
Wesley Cheng

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