Message-ID: <4d2f628e-6adc-5190-61b3-cc9d61f34a84@kernel.org>
Date:   Fri, 31 Mar 2023 14:05:33 +0300
From:   Roger Quadros <rogerq@...nel.org>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc:     "stern@...land.harvard.edu" <stern@...land.harvard.edu>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "vigneshr@...com" <vigneshr@...com>, "srk@...com" <srk@...com>,
        "r-gunasekaran@...com" <r-gunasekaran@...com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 2/2] usb: dwc3: Support
 'snps,gadget-keep-connect-sys-sleep' feature

Hi,

On 23/03/2023 22:51, Thinh Nguyen wrote:
> On Thu, Mar 23, 2023, Roger Quadros wrote:
>>
>>
>> On 23/03/2023 04:17, Thinh Nguyen wrote:
>>> On Wed, Mar 22, 2023, Thinh Nguyen wrote:
>>>> On Wed, Mar 22, 2023, Roger Quadros wrote:
>>>>> On 21/03/2023 21:05, Thinh Nguyen wrote:
>>>>>> On Tue, Mar 21, 2023, Thinh Nguyen wrote:
>>>>>>> On Tue, Mar 21, 2023, Roger Quadros wrote:
>>>>>>>> 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@...nel.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.
>>>>>>>
>>>>>>> You should look into this. These events are important as they can tell
>>>>>>> whether the host initiates resume.
>>>>>>>
>>>>>>>>
>>>>>>>>> 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?
>>>>>>>>
>>>>>>>
>>>>>>> It seems fragile for the implementation to be dependent on platform
>>>>>>> specific feature right?
>>>>>>>
>>>>>>> Also, what will happen in a typical case when the host puts the device
>>>>>>> in suspend and initiates resume while the device is in system suspend
>>>>>>> (and stay in suspend over a period of time)? There is no VBUS change.
>>>>>>> There will be problem if host detects no response from device in time.
>>>>>>>
>>>>>>> Don't we need these events to wakeup the device?
>>>>>
>>>>> That's why the TI implementation has line-state change detection to
>>>>> detect a USB resume. We are doing a out-of-band wake-up. The wake up
>>>>> events are configured in the wrapper driver (dwc3-am62.c).
>>>>>
>>>>> Do you know of any dwc3 implementation that uses in-band mechanism
>>>>> to wake up the System. i.e. it relies on events enabled in DEVTEN register?
>>>>>
>>>>
>>>> We rely on PME. The PME is generated from the PMU of the usb controller
>>>> when it detects a resume. If your platform supports hibernation and if
>>>> the resume signal is connected to the lower layer power manager of your
>>>> device, then you can wakeup the system one level at a time. For example,
>>>> if your device is a pci device, that wakeup signal would tie to the pci
>>>> power manager, waking up the pci layer before waking up the core of the
>>>> usb controller. That's how the host wakes up the host system (e.g. from
>>>> remote wakeup). For this to work, we expect something similar on the
>>>> device side.
>>>>
>>>>>>>
>>>>>>
>>>>>> We may not be able to suspend everything in system suspend for this
>>>>>> case. I'm thinking of treating these events as if they are PME to wakeup
>>>>>> the device, but they are not the same. It may not be simple to handle
>>>>>> this. The lower layers may need to stay awake for the dwc3 to handle
>>>>>> these events. Hm... it gets a bit complicated.
>>>>>
>>>>> As we are going into suspend, we are not really in a position to handle any
>>>>> (DEVTEN) events till we have fully resumed.
>>>>> So yes, we need to rely on platform specific implementation to wake
>>>>> the System on any USB event.
>>>>>
>>>>
>>>> You may be able to detect vbus change through the connector controller.
>>>> However, the usb controller is the one that detects host resume. What
>>>> platform specific implementation do you have outside of the usb
>>>> controller do you have to get around that?
>>>>
>>>> I'm not sure if your platform supports hibernation or if the PME signal
>>>> on your platform can wakeup the system, but currently dwc3 driver
>>>> doesn't handle hibernation (device side). If there's no hibernation,
>>>> there's no PME.
>>
>> No, in this TI SoC, hibernation feature is not supported in the dwc3 core.
>>
>>>>
>>>
>>> Actually, I think the dwc3 core is still on during system suspend for
>>> you right? Then I think we can use the wakeup event to wakeup system
>>> suspend on host resume? You can ignore about PME in this case. You may
>>> need to look into what needs stay awake to allow for handling of the
>>> dwc3 event.
>>
>> But in SoC deep-sleep state, all clocks to the dwc3 core are stopped.
>> So I'm not sure if dwc3 events will work.
>>
> 
> Right, you need to keep those clocks running to detect host resume.
> There's still some power saving through the dwc3 controller's handling
> in suspend. You may have some limited power saving from other suspended
> devices on your setup. However, I don't think we can expect the platform
> to go into deep-sleep and also handle host resume.

Why not? if the PHY can detect the host resume and wake up the SoC it will
work right?

cheers,
-roger

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