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Date: Tue, 16 Jun 2015 09:53:08 +0200 From: Tomeu Vizoso <tomeu.vizoso@...labora.com> To: Stephen Warren <swarren@...dotorg.org> Cc: Linus Walleij <linus.walleij@...aro.org>, "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 28 May 2015 at 17:50, Stephen Warren <swarren@...dotorg.org> wrote: > On 05/28/2015 02:26 AM, Tomeu Vizoso wrote: >> >> On 27 May 2015 at 16:49, Stephen Warren <swarren@...dotorg.org> wrote: >>> >>> On 05/27/2015 08:18 AM, Tomeu Vizoso wrote: >>>> >>>> >>>> On 26 May 2015 at 21:41, 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? >>>>> >>>>> 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. >>>> >>>> >>>> >>>> Actually, I have checked and see that gpio-tegra.c registers 256 >>>> gpios, but pinctrl-tegra124.c adds a range of only 251. I don't really >>>> remember where I got the 250 value from, sorry :( >>>> >>>> I don't see how that would cause any concrete problems, but maybe we >>>> should have a single authoritative source (not sure we can do so >>>> without breaking DT ABI though). >>>> >>>>> Right now, I think we get lucky and pinctrl ends up probing first (or >>>>> at >>>>> least very early) anyway. Somewhat related to this series, I wonder if >>>>> we >>>>> shouldn't add pinctrl client properties to every node in the Tegra DT >>>>> that >>>>> describes a controller that makes use of external pins that are >>>>> affected >>>>> by >>>>> the pinmux. Such a change would guarantee this desired probing order. >>>>> In >>>>> order to preserve the "program the entire pinmux at once" semantics, >>>>> these >>>>> new pinctrl client properties would all need to reference empty states, >>>>> yet >>>>> would still need to exist to represent the dependency. >>>> >>>> >>>> >>>> I think so, but aren't almost all those pins used as gpios? If so, >>>> then such a controller's driver will request the gpio it wants which >>>> will cause the gpio driver to be registered (and hopefully probed) if >>>> needed, which in turn will check that the corresponding pinctrl device >>>> has been registered. Or am I missing something? >>> >>> >>> >>> As you say this probably works out fine for pins that are used as GPIOs. >>> I >>> was thinking more about SFIOs. Take an I2C controller, which doesn't use >>> any >>> GPIOs itself. The pinctrl device should be probed before the I2C device, >>> so >>> that the I2C driver can initiate transactions on the I2C bus during its >>> probe if it wanted to (or at least, clients could initiate transactions >>> at >>> any completely arbitrary time as soon as probe was complete). >> >> >> What is using the SFIO in this case, the I2C master or the I2C client? > > > The I2C controller a/k/a the I2C master. > >> In any case, is the problem you are referring to that ICs may rely on > > > s/ICs/drivers/ I think. > >> a specific pinmux configuration but that's not currently reflected on >> the DT because pinmux configuration happened so early that things just >> worked? > > > Yes; the dependency of some nodes on pinctrl isn't explicitly called out in > the DT. It's probably not a good idea to have such implicit dependencies, > although I suppose for something so central as pinmux, maybe it's not > terrible, since almost everything depends on it and it's pretty obvious. Yup, agreed. Thanks, Tomeu -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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