Re: [PATCH v3 3/3] usb: phy: hold wakeupsource when USB is enumerated in peripheral mode

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 13 July 2015 at 12:30, Peter Chen <peter.chen@xxxxxxxxxxxxx> wrote:
> On Mon, Jul 13, 2015 at 01:26:23PM +0530, Sumit Semwal wrote:
>> Hi Peter,
>>
>> On 8 June 2015 at 14:02, Peter Chen <peter.chen@xxxxxxxxxxxxx> wrote:
>> > On Mon, Jun 08, 2015 at 12:37:00PM +0530, Sumit Semwal wrote:
>> >> H Peter, Felipe,
>> >>
>> >> On 14 January 2015 at 06:56, Peter Chen <peter.chen@xxxxxxxxxxxxx> wrote:
>> >> > On Tue, Jan 13, 2015 at 10:18:02AM -0600, Felipe Balbi wrote:
>> >> >> On Tue, Jan 13, 2015 at 04:02:20PM +0530, Kiran Raparthy wrote:
>> >> >> > Hi Felipe,
>> >> >> >
>> >> >> > On 1 December 2014 at 11:09, Kiran Raparthy <kiran.kumar@xxxxxxxxxx> wrote:
>> >> >> > > Hi Felipe,
>> >> >> > >
>> >> >> > > On 25 November 2014 at 20:15, Felipe Balbi <balbi@xxxxxx> wrote:
>> >> >> > >> On Tue, Nov 25, 2014 at 07:06:18AM +0000, Peter Chen wrote:
>> >> >> > >>>
>> >> >> > >>> >
>> >> >> > >>> > usb: phy: hold wakeupsource when USB is enumerated in peripheral mode
>> >> >> > >>> >
>> >> >> > >>> > Some systems require a mechanism to prevent system to enter into suspend
>> >> >> > >>> > state when USB is connected and enumerated in peripheral mode.
>> >> >> > >>> >
>> >> >> > >>> > This patch provides an interface to hold a wakeupsource to prevent suspend.
>> >> >> > >>> > PHY drivers can use this interface when USB is connected and enumerated in
>> >> >> > >>> > peripheral mode.
>> >> >> > >>> >
>> >> >> > >>> > A timed wakeupsource is temporarily held on USB disconnect events, to allow
>> >> >> > >>> > the rest of the system to react to the USB disconnection (dropping host
>> >> >> > >>> > sessions, updating charger status, etc.) prior to re-allowing suspend.
>> >> >> > >>> >
>> >> >> > >>>
>> <snip>
>> >>
>> >> Kiran is unable to continue on this patch anymore, so despite my very
>> >> limited usb experience, I would like to take this over and with your
>> >> help, take it to closure.
>> >>
>> >> From what I understand, it might be possible to do this either at the
>> >> usb controller driver (where it detects if it has enumerated in host
>> >> mode or device mode) or in the extcon driver (where it detects VBUS
>> >> etc..) -  which would be a cleaner / more logical way to do it?
>> >>
>> >> Thanks for all your help!
>> >
>> > I added my suggestions below:
>> >
>> > My opinion is: if we need this feature, we should depend on gadget's
>> > state, eg 'configured', not vbus level. The system suspend should be
>> > allowed if the gadget state is 'suspended' even vbus is still there.
>> >
>> > And when the gadget goes to suspend or reset or disconnect state, we can
>> > go to disable this wakeup source.
>> >
>> > At drivers/usb/gadget/composite.c, we can know the gadget's state.
>> >
>> Thanks very much for your suggestion, and apologies in the delay in response.
>>
>> I tried to study your suggestion and the code a little bit more, and
>> while I liked your idea quite a bit, I also realised that for the case
>> of letting the USB charger use cases, in gadget framework, there
>> doesn't seem to be a way to get the USB_EVENT_CHARGER, since charger
>> would likely not be a gadget.
>>
>> In this case, how'd we be able to enable / disable wakeup_source for
>> charger events?
>
> We may not prevent the system entering system if it is a charger, isn't
> it, so don't need to consider USB charger.
>
Thanks for your comments, Peter!
>From the Android code that I see, it seems that for a charger
connect/disconnect, some systems might require some time to react to
the change in power, and hence there's a timed-out wakeup event for
USB charger cases. That;s where the consideration for USB chargers
came from.
>>
>> If indeed we can't handle charger events in the way suggested by you,
>> may I propose the following:
>>
>> - implement this in USB-phy as proposed in Kiran's original patch,
>> - keep it disabled by default, and add a module param to enable/disable it
>> - for no vbus case, use another event (USB_EVENT_ENUMERATED /
>> USB_EVENT_NONE? ) to identify connect / disconnect?
>>      (OR, maybe don't do anything for such cases, since most likely
>> the chipidea kind of implementations would handle it themselves?)
>>
>
> In my opinion, we can do noop for wakeup source if it is a USB charger.
>
I think I misunderstood your comment here - do you mean for 'no vbus
case (like chipidea)' do a noop for wakeup source? In the gadget
framework, there doesn't seem to be a way to get to know if a USB
charger is connected.

>> Of course these are based on my limited reading of the USB code, so
>> I'd be grateful if you'd let me know of any obvious gaps in my
>> understanding!
>>
>> > --
>> >
>> > Best Regards,
>> > Peter Chen
>>
>>
>> Best regards,
>> Sumit.
>
> --
>
> Best Regards,
> Peter Chen

Best regards,
Sumit.
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Linux Media]     [Linux Input]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [Old Linux USB Devel Archive]

  Powered by Linux