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

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Message-ID: <20160620085205.GN5809@piout.net>
Date:	Mon, 20 Jun 2016 10:52:05 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
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" <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

On 20/06/2016 at 08:46:02 +0000, Yang, Wenyou wrote :
> Hi Alexandre & Nicolas,
> 
> > -----Original Message-----
> > From: Alexandre Belloni [mailto:alexandre.belloni@...e-electrons.com]
> > Sent: 2016年6月20日 16:04
> > 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 20/06/2016 at 03:16:35 +0000, Yang, Wenyou wrote :
> > > > 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.
> > >
> > 
> > I know but this is irrelevant to this discussion. If you need to use the SFR from
> > another driver you will simply get it from that other driver.
> > 
> > I that case, you will try to get "atmel,sama5d2-sfr". It is only present on sama5d2
> > so you have enough information to know whether or not you can use it to
> > suspend/resume.
> 
> I understand what your meaning :).
> Use "atmel,sama5d2-sfr" compatible to distinguish whether forcibly suspend USB port via SFR or not.
> 
> I am not sure if it is a better solution.
> 

It is definitively superior. There is only one lookup in the device tree
instead of two because whatever happens, you will have to get the SFR
regmap and you don't need to add a compatible string for an IP that
didn't change.

> Nicolas, could you give your opinion?
> 
> > 
> > --
> > Alexandre Belloni, Free Electrons
> > Embedded Linux, Kernel and Android engineering http://free-electrons.com
> 
> 
> Best Regards,
> Wenyou Yang

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