linux-kernel - Re: [PATCH 1/4] mfd: max14577: Add max14577 MFD driver core

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Message-ID: <20131114102419.GE26614@sirena.org.uk>
Date:	Thu, 14 Nov 2013 10:24:19 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Kyungmin Park <kmpark@...radead.org>
Cc:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	Anton Vorontsov <anton@...msg.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH 1/4] mfd: max14577: Add max14577 MFD driver core

On Thu, Nov 14, 2013 at 10:33:22AM +0900, Kyungmin Park wrote:
> On Wed, Nov 13, 2013 at 10:13 PM, Mark Brown <broonie@...nel.org> wrote:

> > Are you *positive* this is a falling triggered IRQ?  All the code to do
> > with spinning reading the GPIO state during handling makes it look like
> > this is in fact an active low interrupt and a lot of the code in here is
> > working around trying to handle that as the wrong kind of IRQ.

> It's not work with level triggering. as wm8994, it requires edge
> triggering. previous time I send RFC patch to handle edge triggering
> at regmap.

No, wm8994 is level triggered only - the edge triggering stuff there is
to work around some SoCs that could only support edge triggering and not
level triggering.  Is this a similar issue or is there something else
going on, what's the differeence with a level triggered scheme?

> >> +static int __init max14577_i2c_init(void)
> >> +{
> >> +     return i2c_add_driver(&max14577_i2c_driver);
> >> +}
> >> +subsys_initcall(max14577_i2c_init);

> > Why not module_i2c_driver?

> there's ordering issue, it should provide regulator which is used
> others before USB probe. if not, it failed to use USB.
> Other PMICs use also subsys_initcall for this reason.

Modern systems should be able to use deferred probing to resolve these
dependencies, subsys_initcall() is mostly there for legacy reasons and
new systems ought to be able to move away from it.

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