linux-kernel - Re: [PATCH 02/21] ARM: tegra: Add gpio-ranges property

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Date:	Tue, 02 Jun 2015 09:40:33 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Stéphane Marchesin 
	<stephane.marchesin@...il.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Alexander Holler <holler@...oftware.de>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Alexandre Courbot <gnurou@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 02/21] ARM: tegra: Add gpio-ranges property

On 06/02/2015 05:28 AM, Linus Walleij wrote:
> On Tue, May 26, 2015 at 9:41 PM, Stephen Warren <swarren@...dotorg.org> wrote:
>> On 05/25/2015 08:53 AM, Tomeu Vizoso wrote:
>>>
>>> Specify how the GPIOs map to the pins in T124, so the dependency is
>>> explicit.
>>>
>>> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
>>> ---
>>>    arch/arm/boot/dts/tegra124.dtsi | 1 +
>>>    1 file changed, 1 insertion(+)
>>>
>>> diff --git a/arch/arm/boot/dts/tegra124.dtsi
>>> b/arch/arm/boot/dts/tegra124.dtsi
>>> index 13cc7ca..5d1d35f 100644
>>> --- a/arch/arm/boot/dts/tegra124.dtsi
>>> +++ b/arch/arm/boot/dts/tegra124.dtsi
>>> @@ -254,6 +254,7 @@
>>>                  gpio-controller;
>>>                  #interrupt-cells = <2>;
>>>                  interrupt-controller;
>>> +               gpio-ranges = <&pinmux 0 0 250>;
>>
>>
>> We should be consistent between SoCs. Why not make the same change for all
>> Tegra SoCs?
>
> Agreed.
>
>> I think this change will cause the GPIO subsystem to call into the pinctrl
>> subsystem and create/add/register a new GPIO<->pinctrl range structure. The
>> pinctrl driver already does this, so I think we'll end up with two duplicate
>> entries in the pinctrl device's gpio_ranges list. This probably won't cause
>> a problem, but I wanted to make sure you'd thought about it to make sure.
>
> That sounds like duplication indeed, I would expect that first a patch
> adds the ranges to the dts[i] files and then a second patch delete the
> same ranges from the pinctrl driver then, if these shall come in from
> the device tree.

We can't delete the gpio-range-registration code from the Tegra pinmux 
driver, or old DTs won't work correctly. We could make it conditional 
based upon whether the DT contains the property or not.

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