linux-kernel - Re: [PATCH 4/9] PCI: mvebu: add support for reset on GPIO

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Date:	Tue, 13 Aug 2013 12:59:40 +0200
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Cc:	Thierry Reding <thierry.reding@...il.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Andrew Lunn <andrew@...n.ch>,
	Russell King <linux@....linux.org.uk>,
	Jason Cooper <jason@...edaemon.net>,
	devicetree@...r.kernel.org, linux-pci@...r.kernel.org,
	Sascha Hauer <s.hauer@...gutronix.de>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 4/9] PCI: mvebu: add support for reset on GPIO

Hi Sebastian,

Am Dienstag, den 13.08.2013, 12:40 +0200 schrieb Sebastian Hesselbarth:
> On 08/13/13 12:03, Thierry Reding wrote:
> > On Tue, Aug 13, 2013 at 10:30:30AM +0200, Thomas Petazzoni wrote:
> >> Dear Thierry Reding,
> >>
> >> On Tue, 13 Aug 2013 10:09:56 +0200, Thierry Reding wrote:
> >>
> >>>> +- reset-gpios: optional gpio to PERST#
> >>>> +- reset-delay-ms: delay in ms to wait after reset de-assertion
> >>>
> >>> I remember some recent discussion about this, and we now have this reset
> >>> framework, so perhaps it makes more sense to use the reset binding for
> >>> this? Cc'ing Stephen (as part of the device tree bindings maintainers
> >>> team) who was involved in that recent reset bindings discussion.
> >>
> >> I also thought about this, but the reset framework seems to be designed
> >> for "reset controller" IPs, i.e special IPs that are controlling reset
> >> signals. Looking at Documentation/devicetree/bindings/reset/reset.txt,
> >> I'm not sure to see how this would apply to GPIO-controlled reset
> >> signals.
> >
> > See:
> >
> > 	http://www.mail-archive.com/devicetree-discuss@lists.ozlabs.org/msg36900.html
> >
> > which seems to have carried over to this at some point:
> >
> > 	http://www.spinics.net/lists/devicetree/msg00521.html
> >
> > Some of the messages in between I can't find in any archive, sorry.
> 
> Thierry, Sascha,
> 
> thanks for the input. Flipping through the above discussion, I guess
> using "reset-gpios" and "reset-delay-us" should be fine?
> 
> I can also remove the delay property for now, as I cannot find a final
> conclusion about the configurable delay.

Yes, I'm in favor of using 'reset-gpios'. If we can agree on this
binding, I'll add support to the reset framework core.

> In the driver, I will stick to bare gpiolib and wait for gpio-reset
> driver to become available. Currently, we don't have sophisticated
> reset handling in pci-mvebu anyway.

Sounds good to me.

regards
Philipp

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