Re: [RFC PATCH 2/2] usb: dwc3: Support 'snps,gadget-keep-connect-sys-sleep' feature

[Roger Quadros <rogerq@kernel.org>]

Hi Thinh,

On 20/03/2023 20:52, Thinh Nguyen wrote:
> Hi,
> 
> On Mon, Mar 20, 2023, Roger Quadros wrote:
>> Implement 'snps,gadget-keep-connect-sys-sleep' property.
>>
>> Do not stop the gadget controller and disconnect if this
>> property is present and we are connected to a USB Host.
>>
>> Prevent System sleep if Gadget is not in USB suspend.
>>
>> Signed-off-by: Roger Quadros <rogerq@kernel.org>
>> ---
>>  drivers/usb/dwc3/core.c   | 25 +++++++++++++++++++------
>>  drivers/usb/dwc3/core.h   |  2 ++
>>  drivers/usb/dwc3/gadget.c | 25 +++++++++++++++++++++++--
>>  3 files changed, 44 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>> index 476b63618511..a47bbaa27302 100644
>> --- a/drivers/usb/dwc3/core.c
>> +++ b/drivers/usb/dwc3/core.c
>> @@ -1575,6 +1575,9 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>>  	dwc->dis_split_quirk = device_property_read_bool(dev,
>>  				"snps,dis-split-quirk");
>>  
>> +	dwc->gadget_keep_connect_sys_sleep = device_property_read_bool(dev,
>> +				"snps,gadget-keep-connect-sys-sleep");
>> +
>>  	dwc->lpm_nyet_threshold = lpm_nyet_threshold;
>>  	dwc->tx_de_emphasis = tx_de_emphasis;
>>  
>> @@ -2027,14 +2030,20 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
>>  {
>>  	unsigned long	flags;
>>  	u32 reg;
>> +	int ret;
>>  
>>  	switch (dwc->current_dr_role) {
>>  	case DWC3_GCTL_PRTCAP_DEVICE:
>>  		if (pm_runtime_suspended(dwc->dev))
>>  			break;
>> -		dwc3_gadget_suspend(dwc);
>> +		ret = dwc3_gadget_suspend(dwc);
>> +		if (ret) {
>> +			dev_err(dwc->dev, "gadget not suspended: %d\n", ret);
>> +			return ret;
>> +		}
>>  		synchronize_irq(dwc->irq_gadget);
>> -		dwc3_core_exit(dwc);
>> +		if(!dwc->gadget_keep_connect_sys_sleep)
>> +			dwc3_core_exit(dwc);
>>  		break;
>>  	case DWC3_GCTL_PRTCAP_HOST:
>>  		if (!PMSG_IS_AUTO(msg) && !device_may_wakeup(dwc->dev)) {
>> @@ -2088,11 +2097,15 @@ static int dwc3_resume_common(struct dwc3 *dwc, pm_message_t msg)
>>  
>>  	switch (dwc->current_dr_role) {
>>  	case DWC3_GCTL_PRTCAP_DEVICE:
>> -		ret = dwc3_core_init_for_resume(dwc);
>> -		if (ret)
>> -			return ret;
>> +		if (!dwc->gadget_keep_connect_sys_sleep)
>> +		{
>> +			ret = dwc3_core_init_for_resume(dwc);
>> +			if (ret)
>> +				return ret;
>> +
>> +			dwc3_set_prtcap(dwc, DWC3_GCTL_PRTCAP_DEVICE);
>> +		}
>>  
>> -		dwc3_set_prtcap(dwc, DWC3_GCTL_PRTCAP_DEVICE);
>>  		dwc3_gadget_resume(dwc);
>>  		break;
>>  	case DWC3_GCTL_PRTCAP_HOST:
>> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
>> index 582ebd9cf9c2..f84bac815bed 100644
>> --- a/drivers/usb/dwc3/core.h
>> +++ b/drivers/usb/dwc3/core.h
>> @@ -1328,6 +1328,8 @@ struct dwc3 {
>>  	unsigned		dis_split_quirk:1;
>>  	unsigned		async_callbacks:1;
>>  
>> +	unsigned		gadget_keep_connect_sys_sleep:1;
>> +
>>  	u16			imod_interval;
>>  
>>  	int			max_cfg_eps;
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 3c63fa97a680..8062e44f63f6 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -4572,12 +4572,23 @@ void dwc3_gadget_exit(struct dwc3 *dwc)
>>  int dwc3_gadget_suspend(struct dwc3 *dwc)
>>  {
>>  	unsigned long flags;
>> +	int link_state;
>>  
>>  	if (!dwc->gadget_driver)
>>  		return 0;
>>  
>> -	dwc3_gadget_run_stop(dwc, false, false);
>> +	if (dwc->gadget_keep_connect_sys_sleep && dwc->connected) {
>> +		link_state = dwc3_gadget_get_link_state(dwc);
>> +		/* Prevent PM Sleep if not in U3/L2 */
>> +		if (link_state != DWC3_LINK_STATE_U3)
>> +			return -EBUSY;
>> +
>> +		/* don't stop/disconnect */
>> +		dwc3_gadget_disable_irq(dwc);
> 
> We shouldn't disable event interrupt here. What will happen if the

Due to some reason, if I don't disable the event interrupts here then
after USB resume the USB controller is malfunctioning.
It no longer responds to any requests from Host.

> device is disconnected and reconnect to the host while the device is
> still in system suspend? The host would not be able to communicate with
> the device then.

In the TI platform, The system is woken up on any VBUS/linestate change
and in dwc3_gadget_resume we enable the events again and check for pending
events. Is it pointless to check for pending events there?

cheers,
-roger

> 
> BR,
> Thinh
> 
>> +		return 0;
>> +	}
>>  
>> +	dwc3_gadget_run_stop(dwc, false, false);
>>  	spin_lock_irqsave(&dwc->lock, flags);
>>  	dwc3_disconnect_gadget(dwc);
>>  	__dwc3_gadget_stop(dwc);
>> @@ -4588,11 +4599,21 @@ int dwc3_gadget_suspend(struct dwc3 *dwc)
>>  
>>  int dwc3_gadget_resume(struct dwc3 *dwc)
>>  {
>> -	int			ret;
>> +	int ret;
>> +	irqreturn_t irq_t;
>>  
>>  	if (!dwc->gadget_driver || !dwc->softconnect)
>>  		return 0;
>>  
>> +	if (dwc->gadget_keep_connect_sys_sleep && dwc->connected) {
>> +		dwc3_gadget_enable_irq(dwc);
>> +		/* check pending events */
>> +		irq_t = dwc3_check_event_buf(dwc->ev_buf);
>> +		if (irq_t == IRQ_WAKE_THREAD)
>> +			dwc3_process_event_buf(dwc->ev_buf);
>> +		return 0;
>> +	}
>> +
>>  	ret = __dwc3_gadget_start(dwc);
>>  	if (ret < 0)
>>  		goto err0;
>> -- 
>> 2.34.1