Re: [PATCH v4 3/3] usb: dwc3: Modify runtime pm ops to handle bus suspend

[Elson Serrao <quic_eserrao@quicinc.com>]

On 10/24/2023 3:14 AM, Roger Quadros wrote:
> Hi Elson,
> 
> On 14/08/2023 21:50, Elson Roy Serrao wrote:
>> The current implementation blocks the runtime pm operations when cable
>> is connected. This would block dwc3 to enter a low power state during
>> bus suspend scenario. Modify the runtime pm ops to handle bus suspend
>> case for such platforms where the controller low power mode entry/exit
>> is handled by the glue driver. This enablement is controlled through a
>> dt property and platforms capable of detecting bus resume can benefit
>> from this feature. Also modify the remote wakeup operations to trigger
>> runtime resume before sending wakeup signal.
>>
>> Signed-off-by: Elson Roy Serrao <quic_eserrao@quicinc.com>
>> ---
>>   drivers/usb/dwc3/core.c   | 28 ++++++++++++++++++++++++++--
>>   drivers/usb/dwc3/core.h   |  3 +++
>>   drivers/usb/dwc3/gadget.c | 32 +++++++++++++++++++++++++-------
>>   3 files changed, 54 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>> index 9c6bf054f15d..9bfd9bb18caf 100644
>> --- a/drivers/usb/dwc3/core.c
>> +++ b/drivers/usb/dwc3/core.c
>> @@ -1518,6 +1518,9 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>>   	dwc->dis_split_quirk = device_property_read_bool(dev,
>>   				"snps,dis-split-quirk");
>>   
>> +	dwc->runtime_suspend_on_usb_suspend = device_property_read_bool(dev,
>> +				"snps,runtime-suspend-on-usb-suspend");
>> +
>>   	dwc->lpm_nyet_threshold = lpm_nyet_threshold;
>>   	dwc->tx_de_emphasis = tx_de_emphasis;
>>   
>> @@ -2029,6 +2032,9 @@ static int dwc3_resume_common(struct dwc3 *dwc, pm_message_t msg)
>>   
>>   	switch (dwc->current_dr_role) {
>>   	case DWC3_GCTL_PRTCAP_DEVICE:
>> +		/* runtime resume on bus resume scenario */
>> +		if (PMSG_IS_AUTO(msg) && dwc->connected)
>> +			break;
>>   		ret = dwc3_core_init_for_resume(dwc);
>>   		if (ret)
>>   			return ret;
>> @@ -2090,8 +2096,13 @@ static int dwc3_runtime_checks(struct dwc3 *dwc)
>>   {
>>   	switch (dwc->current_dr_role) {
>>   	case DWC3_GCTL_PRTCAP_DEVICE:
>> -		if (dwc->connected)
>> +		if (dwc->connected) {
>> +			/* bus suspend scenario */
>> +			if (dwc->runtime_suspend_on_usb_suspend &&
>> +			    dwc->suspended)
> 
> If dwc is already suspended why do we return -EBUSY?
> Should this be !dwc->suspended?
> 

Hi Roger

Thank you for reviewing.
If dwc->suspended is true (i.e suspend event due to U3/L2 is received), 
I am actually breaking from this switch statement and returning 0.

>> +				break;
>>   			return -EBUSY;
>> +		}
>>   		break;
>>   	case DWC3_GCTL_PRTCAP_HOST:
>>   	default:
>> @@ -2107,9 +2118,22 @@ static int dwc3_runtime_suspend(struct device *dev)
>>   	struct dwc3     *dwc = dev_get_drvdata(dev);
>>   	int		ret;
>>   
>> -	if (dwc3_runtime_checks(dwc))
>> +	ret = dwc3_runtime_checks(dwc);
>> +	if (ret)
>>   		return -EBUSY;
>>   
>> +	switch (dwc->current_dr_role) {
>> +	case DWC3_GCTL_PRTCAP_DEVICE:
>> +		/* bus suspend case */
>> +		if (!ret && dwc->connected)
> 
> No need to check !ret again as it will never happen because
> we are returning -EBUSY earlier if (ret);
> 
Thanks for this catch. I will remove !ret check in v5.

>> +			return 0;
>> +		break;
>> +	case DWC3_GCTL_PRTCAP_HOST:
>> +	default:
>> +		/* do nothing */
>> +		break;
>> +	}
>> +
> 
> While this takes care of runtime suspend case, what about system_suspend?
> Should this check be moved to dwc3_suspend_common() instead?
> 

Sure I can move these checks to dwc3_suspend_common to make it generic.
Will rename this patch to "Modify pm ops to handle bus suspend" since 
this is now not limited to only runtime suspend/resume. Will also rename 
dwc->runtime_suspend_on_usb_suspend to dwc->delegate_wakeup_interrupt 
based on earlier feedback.

I am still working on a clean way to enable/disable this feature (i.e 
set dwc->delegate_wakeup_interrupt flag) from the glue driver based on 
Thinh's feedback .
I will accommodate above feedback as well and upload v5.

Thanks
Elson
>>   	ret = dwc3_suspend_common(dwc, PMSG_AUTO_SUSPEND);
>>   	if (ret)
>>   		return ret;
>> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
>> index a69ac67d89fe..f2f788a6b4b5 100644
>> --- a/drivers/usb/dwc3/core.h
>> +++ b/drivers/usb/dwc3/core.h
>> @@ -1124,6 +1124,8 @@ struct dwc3_scratchpad_array {
>>    * @num_ep_resized: carries the current number endpoints which have had its tx
>>    *		    fifo resized.
>>    * @debug_root: root debugfs directory for this device to put its files in.
>> + * @runtime_suspend_on_usb_suspend: true if dwc3 runtime suspend is allowed
>> + *			during bus suspend scenario.
>>    */
>>   struct dwc3 {
>>   	struct work_struct	drd_work;
>> @@ -1340,6 +1342,7 @@ struct dwc3 {
>>   	int			last_fifo_depth;
>>   	int			num_ep_resized;
>>   	struct dentry		*debug_root;
>> +	bool			runtime_suspend_on_usb_suspend;
>>   };
>>   
>>   #define INCRX_BURST_MODE 0
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 5fd067151fbf..978ce0e91164 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -2401,15 +2401,21 @@ static int dwc3_gadget_wakeup(struct usb_gadget *g)
>>   		return -EINVAL;
>>   	}
>>   
>> -	spin_lock_irqsave(&dwc->lock, flags);
>>   	if (!dwc->gadget->wakeup_armed) {
>>   		dev_err(dwc->dev, "not armed for remote wakeup\n");
>> -		spin_unlock_irqrestore(&dwc->lock, flags);
>>   		return -EINVAL;
>>   	}
>> -	ret = __dwc3_gadget_wakeup(dwc, true);
>>   
>> +	ret = pm_runtime_resume_and_get(dwc->dev);
>> +	if (ret < 0) {
>> +		pm_runtime_set_suspended(dwc->dev);
>> +		return ret;
>> +	}
>> +
>> +	spin_lock_irqsave(&dwc->lock, flags);
>> +	ret = __dwc3_gadget_wakeup(dwc, true);
>>   	spin_unlock_irqrestore(&dwc->lock, flags);
>> +	pm_runtime_put_noidle(dwc->dev);
>>   
>>   	return ret;
>>   }
>> @@ -2428,6 +2434,12 @@ static int dwc3_gadget_func_wakeup(struct usb_gadget *g, int intf_id)
>>   		return -EINVAL;
>>   	}
>>   
>> +	ret = pm_runtime_resume_and_get(dwc->dev);
>> +	if (ret < 0) {
>> +		pm_runtime_set_suspended(dwc->dev);
>> +		return ret;
>> +	}
>> +
>>   	spin_lock_irqsave(&dwc->lock, flags);
>>   	/*
>>   	 * If the link is in U3, signal for remote wakeup and wait for the
>> @@ -2438,6 +2450,7 @@ static int dwc3_gadget_func_wakeup(struct usb_gadget *g, int intf_id)
>>   		ret = __dwc3_gadget_wakeup(dwc, false);
>>   		if (ret) {
>>   			spin_unlock_irqrestore(&dwc->lock, flags);
>> +			pm_runtime_put_noidle(dwc->dev);
>>   			return -EINVAL;
>>   		}
>>   		dwc3_resume_gadget(dwc);
>> @@ -2452,6 +2465,7 @@ static int dwc3_gadget_func_wakeup(struct usb_gadget *g, int intf_id)
>>   		dev_err(dwc->dev, "function remote wakeup failed, ret:%d\n", ret);
>>   
>>   	spin_unlock_irqrestore(&dwc->lock, flags);
>> +	pm_runtime_put_noidle(dwc->dev);
>>   
>>   	return ret;
>>   }
>> @@ -2732,21 +2746,23 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
>>   	/*
>>   	 * Avoid issuing a runtime resume if the device is already in the
>>   	 * suspended state during gadget disconnect.  DWC3 gadget was already
>> -	 * halted/stopped during runtime suspend.
>> +	 * halted/stopped during runtime suspend except for bus suspend case
>> +	 * where we would have skipped the controller halt.
>>   	 */
>>   	if (!is_on) {
>>   		pm_runtime_barrier(dwc->dev);
>> -		if (pm_runtime_suspended(dwc->dev))
>> +		if (pm_runtime_suspended(dwc->dev) && !dwc->connected)
>>   			return 0;
>>   	}
>>   
>>   	/*
>>   	 * Check the return value for successful resume, or error.  For a
>>   	 * successful resume, the DWC3 runtime PM resume routine will handle
>> -	 * the run stop sequence, so avoid duplicate operations here.
>> +	 * the run stop sequence except for bus resume case, so avoid
>> +	 * duplicate operations here.
>>   	 */
>>   	ret = pm_runtime_get_sync(dwc->dev);
>> -	if (!ret || ret < 0) {
>> +	if ((!ret && !dwc->connected) || ret < 0) {
>>   		pm_runtime_put(dwc->dev);
>>   		if (ret < 0)
>>   			pm_runtime_set_suspended(dwc->dev);
>> @@ -4331,6 +4347,8 @@ static void dwc3_gadget_suspend_interrupt(struct dwc3 *dwc,
>>   	}
>>   
>>   	dwc->link_state = next;
>> +	pm_runtime_mark_last_busy(dwc->dev);
>> +	pm_request_autosuspend(dwc->dev);
>>   }
>>   
>>   static void dwc3_gadget_interrupt(struct dwc3 *dwc,
>