linux-kernel - Re: [PATCH V4] usb: remove unnecessary CONFIG_PM dependency from USB

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Date:	Tue, 1 Dec 2015 08:25:55 -0600
From:	Felipe Balbi <balbi@...com>
To:	Li Jun <b47624@...escale.com>
CC:	Peter Chen <peter.chen@...escale.com>,
	Nathan Sullivan <nathan.sullivan@...com>,
	<gregkh@...uxfoundation.org>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V4] usb: remove unnecessary CONFIG_PM dependency from USB_OTG


Hi Li,

Li Jun <b47624@...escale.com> writes:
>> > I am sorry I did not consider the legacy OTG design, this patch should
>> > be dropped.
>> 
>> there is no "legacy" OTG design. OTG requires a bus suspend to enter
>> HNP, and that's achieved by stopping all transfers and avoid new URB
>> submission so usbcore can put the bus in suspend (by means of USB
>> autosuspend). If you're bypassing that in the OTG FSM thing, that needs
>> to be fixed ASAP as that makes it a lot harder for any generic changes
>> in usbcore to be validated. Specially when you consider not many will
>> have whatever special HW which, likely, doesn't even work with mainline
>> to validate a change.
>> 
>> Please, make sure to fix that design so that HNP *always* goes through
>> the proper code path. If you have devices which would prevent HNP
>> because their class driver (host side driver) would never autosuspend,
>> fix that as well.
>> 
>
> Hi Felipe
>
> I am going to fix this as you suggested, for those interface drivers which
> do not support autosuspend, should we
> - Fix its driver by enable autosuspend and adding suspend()&resume()? or
> - Unbind its interface before autosuspend the usb device?

IMO it's best if you could add proper autosuspend device to such drivers.

-- 
balbi

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