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

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Message-ID: <20151104030056.GA20460@shlinux2>
Date:	Wed, 4 Nov 2015 11:00:58 +0800
From:	Peter Chen <peter.chen@...escale.com>
To:	Felipe Balbi <balbi@...com>
CC:	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

On Tue, Nov 03, 2015 at 07:56:55AM -0600, Felipe Balbi wrote:
> 
> Hi,
> 
> Nathan Sullivan <nathan.sullivan@...com> writes:
> > The USB OTG support currently depends on power management
> > (CONFIG_PM) being enabled, but does not actually need it enabled.
> > Remove this dependency.
> >
> > Tested on Bay Trail hardware with dwc3 USB.
> >
> > Signed-off-by: Nathan Sullivan <nathan.sullivan@...com>
> > ---
> >  drivers/usb/core/Kconfig |    1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
> > index a99c89e..9c5cdf3 100644
> > --- a/drivers/usb/core/Kconfig
> > +++ b/drivers/usb/core/Kconfig
> > @@ -43,7 +43,6 @@ config USB_DYNAMIC_MINORS
> >  
> >  config USB_OTG
> >  	bool "OTG support"
> > -	depends on PM
> 
> I don't think this is correct. OTG depends on USB bus suspend, which is
> only available on PM builds. Care to further detail why you think PM is
> not needed on OTG ?
> 

OTG depends on USB bus suspend is not a must, the hardware controlled OTG
design do HNP when the bus goes to suspend; but if the software
implements OTG FSM, it is the user option whether do HNP, and bus
suspend is controlled by OTG FSM software (stop SOF), but not by host 
stack (eg, ehci).

I am sorry I did not consider the legacy OTG design, this patch should
be dropped.

-- 

Best Regards,
Peter Chen
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