usb: dwc3: gadget: Change runtime pm function for DWC3 runtime suspend

usb: dwc3: gadget: Change runtime pm function for DWC3 runtime suspend

[Daehwan Jung]

It seems pm_runtime_put calls runtime_idle callback not runtime_suspend callback.
It's better to use pm_runtime_put_sync_suspend to allow DWC3 runtime suspend.

Signed-off-by: Daehwan Jung <dh10.jung@samsung.com>
---
 drivers/usb/dwc3/gadget.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index aebcf8e..4a4b93b 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2229,7 +2229,7 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 	 */
 	ret = pm_runtime_get_sync(dwc->dev);
 	if (!ret || ret < 0) {
-		pm_runtime_put(dwc->dev);
+		pm_runtime_put_sync_suspend(dwc->dev);
 		return 0;
 	}
 
-- 
2.7.4

Re: usb: dwc3: gadget: Change runtime pm function for DWC3 runtime suspend

[Sergei Shtylyov]

Hello!

On 15.02.2021 5:38, Daehwan Jung wrote:

> It seems pm_runtime_put calls runtime_idle callback not runtime_suspend callback.
> It's better to use pm_runtime_put_sync_suspend to allow DWC3 runtime suspend.
> 
> Signed-off-by: Daehwan Jung <dh10.jung@samsung.com>
> ---
>   drivers/usb/dwc3/gadget.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index aebcf8e..4a4b93b 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -2229,7 +2229,7 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
>   	 */
>   	ret = pm_runtime_get_sync(dwc->dev);
>   	if (!ret || ret < 0) {

    BTW, this can be shortened to (ret <= 0)...

> -		pm_runtime_put(dwc->dev);
> +		pm_runtime_put_sync_suspend(dwc->dev);
>   		return 0;
>   	}
>   

MBR, Sergei

Re: usb: dwc3: gadget: Change runtime pm function for DWC3 runtime suspend

[Alan Stern]

On Mon, Feb 15, 2021 at 11:38:58AM +0900, Daehwan Jung wrote:
> It seems pm_runtime_put calls runtime_idle callback not runtime_suspend callback.

How is this fact related to your patch?

> It's better to use pm_runtime_put_sync_suspend to allow DWC3 runtime suspend.

Why do you think it is better?  The advantage of pm_runtime_put is that 
it allows the suspend to occur at a later time in a workqueue thread, so 
the caller doesn't have to wait for the device to go into suspend.

Alan Stern

> Signed-off-by: Daehwan Jung <dh10.jung@samsung.com>
> ---
>  drivers/usb/dwc3/gadget.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index aebcf8e..4a4b93b 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -2229,7 +2229,7 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
>  	 */
>  	ret = pm_runtime_get_sync(dwc->dev);
>  	if (!ret || ret < 0) {
> -		pm_runtime_put(dwc->dev);
> +		pm_runtime_put_sync_suspend(dwc->dev);
>  		return 0;
>  	}
>  
> -- 
> 2.7.4
> 

Re: usb: dwc3: gadget: Change runtime pm function for DWC3 runtime suspend

[Jung Daehwan]

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Hello, Alan

On Mon, Feb 15, 2021 at 12:41:45PM -0500, Alan Stern wrote:
> On Mon, Feb 15, 2021 at 11:38:58AM +0900, Daehwan Jung wrote:
> > It seems pm_runtime_put calls runtime_idle callback not runtime_suspend callback.
> 
> How is this fact related to your patch?

I think we should cause dwc3_runtime_suspend at the time.
That's why I use pm_runtime_put_sync_suspend.

> 
> > It's better to use pm_runtime_put_sync_suspend to allow DWC3 runtime suspend.
> 
> Why do you think it is better?  The advantage of pm_runtime_put is that 
> it allows the suspend to occur at a later time in a workqueue thread, so 
> the caller doesn't have to wait for the device to go into suspend.
> 

We can assume DWC3 was already in suspend state if pm_runtime_get_sync
returns 0. DWC3 resumes due to pm_rumtime_get_sync but it doesn't
re-enter runtime_suspend but runtime_idle. pm_runtime_put decreases
usage_count but doesn't cause runtime_suspend.

1. USB disconnected
2. UDC unbinded
3. DWC3 runtime suspend
4. UDC binded unexpectedly
5. DWC3 runtime resume (pm_runtime_get_sync)
6. DWC3 runtime idle (pm_runtime_put)
   -> DWC3 runtime suspend again (pm_runtime_put_sync_suspend)

I've talked with Wesley in other patch.

usbb: dwc3: gadget: skip pullup and set_speed after suspend
patchwork.kernel.org/project/linux-usb/patch/1611113968-102424-1-git-send-email-dh10.jung@samsung.com

@ Wesley

I think We should guarantee DWC3 enters suspend again at the time.
How do you think?

Best Regards,
Jung Daehwan

> Alan Stern
> 


> > Signed-off-by: Daehwan Jung <dh10.jung@samsung.com>
> > ---
> >  drivers/usb/dwc3/gadget.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> > index aebcf8e..4a4b93b 100644
> > --- a/drivers/usb/dwc3/gadget.c
> > +++ b/drivers/usb/dwc3/gadget.c
> > @@ -2229,7 +2229,7 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
> >  	 */
> >  	ret = pm_runtime_get_sync(dwc->dev);
> >  	if (!ret || ret < 0) {
> > -		pm_runtime_put(dwc->dev);
> > +		pm_runtime_put_sync_suspend(dwc->dev);
> >  		return 0;
> >  	}
> >  
> > -- 
> > 2.7.4
> > 
> 

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]

Re: usb: dwc3: gadget: Change runtime pm function for DWC3 runtime suspend

[Alan Stern]

On Tue, Feb 16, 2021 at 10:30:52AM +0900, Jung Daehwan wrote:
> Hello, Alan
> 
> On Mon, Feb 15, 2021 at 12:41:45PM -0500, Alan Stern wrote:
> > On Mon, Feb 15, 2021 at 11:38:58AM +0900, Daehwan Jung wrote:
> > > It seems pm_runtime_put calls runtime_idle callback not runtime_suspend callback.
> > 
> > How is this fact related to your patch?
> 
> I think we should cause dwc3_runtime_suspend at the time.

Why do you think so?

> That's why I use pm_runtime_put_sync_suspend.
> 
> > 
> > > It's better to use pm_runtime_put_sync_suspend to allow DWC3 runtime suspend.
> > 
> > Why do you think it is better?  The advantage of pm_runtime_put is that 
> > it allows the suspend to occur at a later time in a workqueue thread, so 
> > the caller doesn't have to wait for the device to go into suspend.
> > 
> 
> We can assume DWC3 was already in suspend state if pm_runtime_get_sync
> returns 0. DWC3 resumes due to pm_rumtime_get_sync but it doesn't
> re-enter runtime_suspend but runtime_idle. pm_runtime_put decreases
> usage_count but doesn't cause runtime_suspend.
> 
> 1. USB disconnected
> 2. UDC unbinded
> 3. DWC3 runtime suspend
> 4. UDC binded unexpectedly
> 5. DWC3 runtime resume (pm_runtime_get_sync)
> 6. DWC3 runtime idle (pm_runtime_put)
>    -> DWC3 runtime suspend again (pm_runtime_put_sync_suspend)

That's what happens with your patch.  Now look at what happens without 
the patch:

1. USB disconnected
2. UDC unbound
3. DWC3 suspend request is added to waitqueue
4. UDC bound unexpectedly
5. DWC3 suspend request is removed from waitqueue
6. DWC3 runtime idle
7. DWC3 runtime suspend

The difference is that this way, we avoid doing an unnecessary suspend 
and resume, and we save the time they would have required.

> I've talked with Wesley in other patch.
> 
> usbb: dwc3: gadget: skip pullup and set_speed after suspend
> patchwork.kernel.org/project/linux-usb/patch/1611113968-102424-1-git-send-email-dh10.jung@samsung.com
> 
> @ Wesley
> 
> I think We should guarantee DWC3 enters suspend again at the time.

Why do you think we should guarantee this?

Alan Stern

Re: usb: dwc3: gadget: Change runtime pm function for DWC3 runtime suspend

[Wesley Cheng]

On 2/15/2021 5:30 PM, Jung Daehwan wrote:
> Hello, Alan
> 
> On Mon, Feb 15, 2021 at 12:41:45PM -0500, Alan Stern wrote:
>> On Mon, Feb 15, 2021 at 11:38:58AM +0900, Daehwan Jung wrote:
>>> It seems pm_runtime_put calls runtime_idle callback not runtime_suspend callback.
>>
>> How is this fact related to your patch?
> 
> I think we should cause dwc3_runtime_suspend at the time.
> That's why I use pm_runtime_put_sync_suspend.
> 
>>
>>> It's better to use pm_runtime_put_sync_suspend to allow DWC3 runtime suspend.
>>
>> Why do you think it is better?  The advantage of pm_runtime_put is that 
>> it allows the suspend to occur at a later time in a workqueue thread, so 
>> the caller doesn't have to wait for the device to go into suspend.
>>
> 
> We can assume DWC3 was already in suspend state if pm_runtime_get_sync
> returns 0. DWC3 resumes due to pm_rumtime_get_sync but it doesn't
> re-enter runtime_suspend but runtime_idle. pm_runtime_put decreases
> usage_count but doesn't cause runtime_suspend.
> 
> 1. USB disconnected
> 2. UDC unbinded
> 3. DWC3 runtime suspend
> 4. UDC binded unexpectedly
> 5. DWC3 runtime resume (pm_runtime_get_sync)
> 6. DWC3 runtime idle (pm_runtime_put)
>    -> DWC3 runtime suspend again (pm_runtime_put_sync_suspend)
> 
> I've talked with Wesley in other patch.
> 
> usbb: dwc3: gadget: skip pullup and set_speed after suspend
> patchwork.kernel.org/project/linux-usb/patch/1611113968-102424-1-git-send-email-dh10.jung@samsung.com
> 
> @ Wesley
> 
> I think We should guarantee DWC3 enters suspend again at the time.
> How do you think?
> 
Hi Daehwan,

Even if we call runtime idle versus suspend, if the device is still in
the disconnected state, it should call the runtime PM suspend routine
after the autosuspend timer expires.  As Alan mentioned already, this
allows not blocking the caller for the entire DWC3 suspend sequence to
execute. (DWC3 core will suspend other components as well, such as PHYs)

Also, for legitimate cases where pullup is actually called to start
enumeration from a suspended state, I'm not sure if the short duration
between RS set and re-suspend (due to your patch) is enough time for the
host to actually detect the device connected.

Thanks
Wesley Cheng

> Best Regards,
> Jung Daehwan
> 
>> Alan Stern
>>
> 
> 
>>> Signed-off-by: Daehwan Jung <dh10.jung@samsung.com>
>>> ---
>>>  drivers/usb/dwc3/gadget.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>> index aebcf8e..4a4b93b 100644
>>> --- a/drivers/usb/dwc3/gadget.c
>>> +++ b/drivers/usb/dwc3/gadget.c
>>> @@ -2229,7 +2229,7 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
>>>  	 */
>>>  	ret = pm_runtime_get_sync(dwc->dev);
>>>  	if (!ret || ret < 0) {
>>> -		pm_runtime_put(dwc->dev);
>>> +		pm_runtime_put_sync_suspend(dwc->dev);
>>>  		return 0;
>>>  	}
>>>  
>>> -- 
>>> 2.7.4
>>>
>>
>>

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