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 13:12:47 +0300
From:	Felipe Balbi <balbi@...nel.org>
To:	Baolin Wang <baolin.wang@...aro.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


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.

Thanks a lot for testing on your side :-)

-- 
balbi

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