linux-kernel - RE: [PATCH v3 1/2] usb: ohci-at91: Forcibly suspend ports while USB suspend

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Date:	Fri, 10 Jun 2016 08:58:41 +0000
From:	"Yang, Wenyou" <Wenyou.Yang@...el.com>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Ferre, Nicolas" <Nicolas.FERRE@...el.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Brown <broonie@...nel.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	"Kernel development list" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	USB list <linux-usb@...r.kernel.org>
Subject: RE: [PATCH v3 1/2] usb: ohci-at91: Forcibly suspend ports while USB
 suspend

Hi Alan, 

> -----Original Message-----
> From: Alan Stern [mailto:stern@...land.harvard.edu]
> Sent: 2016年6月9日 3:14
> To: Yang, Wenyou <Wenyou.Yang@...el.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>; Ferre, Nicolas
> <Nicolas.FERRE@...el.com>; Rob Herring <robh+dt@...nel.org>; Pawel Moll
> <pawel.moll@....com>; Mark Brown <broonie@...nel.org>; Ian Campbell
> <ijc+devicetree@...lion.org.uk>; Kumar Gala <galak@...eaurora.org>;
> Alexandre Belloni <alexandre.belloni@...e-electrons.com>; Kernel development
> list <linux-kernel@...r.kernel.org>; devicetree@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org; USB list <linux-usb@...r.kernel.org>
> Subject: Re: [PATCH v3 1/2] usb: ohci-at91: Forcibly suspend ports while USB
> suspend
> 
> On Wed, 8 Jun 2016, Wenyou Yang wrote:
> 
> > In order to the save power consumption, as a workaround, suspend
> > forcibly the USB PORTA/B/C via set the SUSPEND_A/B/C bits of OHCI
> > Interrupt Configuration Register in the SFRs while OHCI USB suspend.
> >
> > This suspend operation must be done before the USB clock is disabled,
> > resume after the USB clock is enabled.
> >
> > Signed-off-by: Wenyou Yang <wenyou.yang@...el.com>
> > ---
> 
> You never answered the questions I posted for the first version of this
> patch:
> 
> What does this mean?  What does suspending a port do?  Is it the same as a
> normal USB port suspend?
> 
> If it is the same, why doesn't the USB_PORT_FEAT_SUSPEND subcase of the
> SetPortFeature case in ohci_hub_control() already take care of this?

I remembered I answered your questions, http://lists.infradead.org/pipermail/linux-arm-kernel/2016-May/429245.html

Maybe not very clear.

> 
> Alan Stern


Best Regards,
Wenyou Yang