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

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Date:	Tue, 13 Aug 2013 12:40:29 +0200
From:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
To:	Thierry Reding <thierry.reding@...il.com>
CC:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Russell King <linux@....linux.org.uk>,
	Jason Cooper <jason@...edaemon.net>,
	Andrew Lunn <andrew@...n.ch>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-pci@...r.kernel.org, Sascha Hauer <s.hauer@...gutronix.de>
Subject: Re: [PATCH 4/9] PCI: mvebu: add support for reset on GPIO

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.

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.

Sebastian

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