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

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Date:	Mon, 20 Jun 2016 03:16:35 +0000
From:	"Yang, Wenyou" <Wenyou.Yang@...el.com>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
CC:	Rob Herring <robh@...nel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Ferre, Nicolas" <Nicolas.FERRE@...el.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Brown <broonie@...nel.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	"Kumar Gala" <galak@...eaurora.org>,
	"linux-kernel@...r.kernel.org" <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>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: RE: [PATCH v3 1/2] usb: ohci-at91: Forcibly suspend ports while USB
 suspend

Hi Aleandre,

> -----Original Message-----
> From: Alexandre Belloni [mailto:alexandre.belloni@...e-electrons.com]
> Sent: 2016年6月17日 21:55
> To: Yang, Wenyou <Wenyou.Yang@...el.com>
> Cc: Rob Herring <robh@...nel.org>; Alan Stern <stern@...land.harvard.edu>;
> Greg Kroah-Hartman <gregkh@...uxfoundation.org>; Ferre, Nicolas
> <Nicolas.FERRE@...el.com>; Pawel Moll <pawel.moll@....com>; Mark Brown
> <broonie@...nel.org>; Ian Campbell <ijc+devicetree@...lion.org.uk>; Kumar
> Gala <galak@...eaurora.org>; linux-kernel@...r.kernel.org;
> devicetree@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
> usb@...r.kernel.org
> Subject: Re: [PATCH v3 1/2] usb: ohci-at91: Forcibly suspend ports while USB
> suspend
> 
> On 17/06/2016 at 13:44:22 +0000, Yang, Wenyou wrote :
> > Hi Alexandre,
> >
> > > -----Original Message-----
> > > From: Alexandre Belloni
> > > [mailto:alexandre.belloni@...e-electrons.com]
> > > Sent: 2016年6月9日 4:38
> > > To: Rob Herring <robh@...nel.org>
> > > Cc: Yang, Wenyou <Wenyou.Yang@...el.com>; Alan Stern
> > > <stern@...land.harvard.edu>; Greg Kroah-Hartman
> > > <gregkh@...uxfoundation.org>; Ferre, Nicolas
> > > <Nicolas.FERRE@...el.com>; Pawel Moll <pawel.moll@....com>; Mark
> > > Brown <broonie@...nel.org>; Ian Campbell
> > > <ijc+devicetree@...lion.org.uk>; Kumar Gala <galak@...eaurora.org>;
> > > linux-kernel@...r.kernel.org; devicetree@...r.kernel.org; linux-arm-
> > > kernel@...ts.infradead.org; linux-usb@...r.kernel.org
> > > Subject: Re: [PATCH v3 1/2] usb: ohci-at91: Forcibly suspend ports
> > > while USB suspend
> > >
> > > On 08/06/2016 at 15:26:51 -0500, Rob Herring wrote :
> > > > On Wed, Jun 08, 2016 at 12:15:10PM +0800, 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>
> > > > > ---
> > > > >
> > > > > Changes in v3:
> > > > >  - Change the compatible description for more precise.
> > > > >
> > > > > Changes in v2:
> > > > >  - Add compatible to support forcibly suspend the ports.
> > > > >  - Add soc/at91/at91_sfr.h to accommodate the defines.
> > > > >  - Add error checking for .sfr_regmap.
> > > > >  - Remove unnecessary regmap_read() statement.
> > > > >
> > > > >  .../devicetree/bindings/usb/atmel-usb.txt          |  6 +-
> > > > >  drivers/usb/host/ohci-at91.c                       | 80
> +++++++++++++++++++++-
> > > > >  include/soc/at91/at91_sfr.h                        | 29 ++++++++
> > > > >  3 files changed, 112 insertions(+), 3 deletions(-)  create mode
> > > > > 100644 include/soc/at91/at91_sfr.h
> > > > >
> > > > > diff --git a/Documentation/devicetree/bindings/usb/atmel-usb.txt
> > > > > b/Documentation/devicetree/bindings/usb/atmel-usb.txt
> > > > > index 5883b73..888deaa 100644
> > > > > --- a/Documentation/devicetree/bindings/usb/atmel-usb.txt
> > > > > +++ b/Documentation/devicetree/bindings/usb/atmel-usb.txt
> > > > > @@ -3,8 +3,10 @@ Atmel SOC USB controllers  OHCI
> > > > >
> > > > >  Required properties:
> > > > > - - compatible: Should be "atmel,at91rm9200-ohci" for USB controllers
> > > > > -   used in host mode.
> > > > > + - compatible: Should be one of the following
> > > > > +	       "atmel,at91rm9200-ohci" for USB controllers used in host
> mode.
> > > > > +	       "atmel,sama5d2-ohci" for USB controllers used in host mode
> > > > > +	       on SAMA5D2 which can force to suspend.
> > > >
> > > > Guess I wasn't clear enough before. Drop "which can force to suspend".
> > > >
> > >
> > > Well, my point is that we don't need a new compatible anyway.
> >
> > Could you give some advice?.
> >
> 
> Sure, what I mean is that you can try to get the regmap for the SFR in every case.
> Depending on whether you were able to get it, you can decide to call
> ohci_at91_port_suspend/resume or not (just test for sfr_regmap != NULL).

I don't think so. The SFR includes a lot of miscellaneous functions, more than this one.

> 
> --
> Alexandre Belloni, Free Electrons
> Embedded Linux, Kernel and Android engineering http://free-electrons.com


Best Regards,
Wenyou Yang