On Wed, Oct 29, 2014 at 11:41:22AM -0500, Benoit Parrot wrote: > Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote on Wed [2014-Oct-29 11:45:59 +0100]: > > Hi, > > > > On Tue, Oct 21, 2014 at 03:09:58PM -0500, Benoit Parrot wrote: > > > Based on Boris Brezillion work this is a reworked patch > > > of his initial GPIO hogging mechanism. > > > This patch provides a way to initally configure specific GPIO > > > when the gpio controller is probe. > > > > > > The actual DT scanning to collect the GPIO specific data is performed > > > as part of the gpiochip_add(). > > > > > > The purpose of this is to allows specific GPIOs to be configured > > > without any driver specific code. > > > This particularly usueful because board design are getting > > > increassingly complex and given SoC pins can now have upward > > > of 10 mux values a lot of connections are now dependent on > > > external IO muxes to switch various modes and combination. > > > > > > Specific drivers should not necessarily need to be aware of > > > what accounts to a specific board implementation. This board level > > > "description" should be best kept as part of the dts file. > > > > > > Signed-off-by: Benoit Parrot <bparrot@xxxxxx> > > > > I've been thinking about this for quite some time, it's good to see > > some progress on that :) > > > > However, I have a slightly different use case for it: the Allwinner > > SoCs have a vdd pin coming in for every gpio bank. Nothing out of the > > ordinary so far, except that some of the boards are using a > > GPIO-controlled regulator to feed another bank vdd. That obviously > > causes a chicken-egg issue, since for the gpio-regulator driver to > > probe, it needs to gpio driver, and for the gpio driver to probe, it > > needs the regulator driver. > > Unless the gpio controlling the vdd pin is from the same bank your > trying to power up I do not see the issue here. Not the same bank, but the same driver. -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com
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