linux-kernel - Re: [PATCH] dwc3: gadget: Defer starting the gadget device until gadget is power on

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Date:	Wed, 18 May 2016 18:17:47 +0800
From:	Baolin Wang <baolin.wang@...aro.org>
To:	Felipe Balbi <balbi@...nel.org>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Mark Brown <broonie@...nel.org>,
	USB <linux-usb@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dwc3: gadget: Defer starting the gadget device until
 gadget is power on

On 18 May 2016 at 18:12, Felipe Balbi <balbi@...nel.org> wrote:
>
> Hi,
>
> Baolin Wang <baolin.wang@...aro.org> writes:
>>>> Baolin Wang <baolin.wang@...aro.org> writes:
>>>>>>>>> Make sense.
>>>>>>>>
>>>>>>>> cool, if you wanna work on it, let me know and I can give some details
>>>>>>>> of what I have in mind.
>>>>>>>
>>>>>>> Could you explain details to me, and I wanna continue to optimize the
>>>>>>> power management things. Thanks.
>>>>>>
>>>>>> I have it half-way done. Have a look at my dwc3-fix-suspend branch on
>>>>>> k.org. I haven't sent because I'm not getting a PME event. Can you test
>>>>>> on your end and let me know what happens?
>>
>> I applied some patches (showing below) about suspend/resume at your
>> dwc3-fix-suspend branch with my glue layer runtime_* callbacks on my
>> testing platform.
>> usb: dwc3: implement runtime PM
>> usb: dwc3: core: simplify suspend/resume operations
>> usb: dwc3: core: re-factor init and exit paths
>> usb: dwc3: core: get rid of DWC3_PM_OPS macro
>> usb: dwc3: gadget: fix gadget suspend/resume
>> usb: dwc3: gadget: re-factor ->udc_start and ->udc_stop
>>
>> Then I tested the cable connect/disconnect action to see the dwc core
>> resume/suspend. It looks work well on my platform, except that I did
>> some extra 2 modifications like below:
>> (1)
>> @@ -1485,16 +1490,11 @@ static int dwc3_gadget_run_stop(struct dwc3
>> *dwc, int is_on, int suspend)
>>  {
>>         u32                     reg;
>>         u32                     timeout = 500, i;
>>
>> +       if (pm_runtime_suspended(dwc->dev))
>> +               return 0;
>>
>> (2)
>> @@ -1748,15 +1754,25 @@ static int dwc3_gadget_start(struct usb_gadget *g,
>>          * even though host mode might be active. Don't actually perform
>>          * device-specific initialization until device mode is activated.
>>          */
>>
>> +       if (pm_runtime_suspended(dwc->dev)) {
>> +               spin_unlock_irqrestore(&dwc->lock, flags);
>> +               return 0;
>> +       }
>>
>> +       ret = __dwc3_gadget_start(dwc);
>> +       if (ret)
>> +               goto err1;
>>
>> So I think the dwc3 core can enter suspend mode before gadget function
>> is ready to call the 'usb_gadget_udc_start()' and
>> 'usb_udc_connect_control()', then if the dwc3 core has entered
>> suspended mode, we need to return success when starting the gadget,
>> and leave the gadget starting action from gadget resume. What do you
>> think about that? Thanks.
>
> Well, if this makes it work properly. Then, yeah; looks okay to me. I'll
> add this to the patch introducing runtime PM.

OK.

>
> Thanks a lot for testing on your side :-)

You are welcome:)

>
> --
> balbi



-- 
Baolin.wang
Best Regards