linux-kernel - Re: [PATCH v2 1/4] ARM: dts: omap4-panda: Add USB Host support

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Message-ID: <20130619124412.GC5523@atomide.com>
Date:	Wed, 19 Jun 2013 05:44:13 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Benoit Cousson <b-cousson@...com>
Cc:	Roger Quadros <rogerq@...com>, linux-omap@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] ARM: dts: omap4-panda: Add USB Host support

* Benoit Cousson <b-cousson@...com> [130619 05:41]:
> Hi Tony,
> 
> On 06/19/2013 07:27 AM, Tony Lindgren wrote:
> >* Benoit Cousson <b-cousson@...com> [130619 03:17]:
> >>On 06/19/2013 02:46 AM, Tony Lindgren wrote:
> >>>
> >>>We have a similar issue with the MMC1 PBIAS. I think in the long run we
> >>>should expand regulator (and possibly pinctrl) framework(s) to handle
> >>>comparators. We could just assume that a comparatator is a regulator,
> >>>and have a comparator binding that just uses the regulator code.
> >>
> >>In the case of pbias, the pinctrl seems to be a much better fit for
> >>my point of view. pinctrl can handle pin configuration and this is
> >>what the pbias is in the case of MMC pins.
> >
> >Well just recently Linus W specifically wanted us to use regulator
> >framework for the MMC1 PBIAS rather than pinctrl. That's because
> >from consumer driver point of view, it changes voltage and there's
> >a delay involved. So I guess no conclusion yet, and it's best to
> >do stand alone drivers to deal with those that use pinctrl for the
> >pinctrl specific parts and export it as a regulator for the consumer
> >devices.
> 
> In the case of pbias, the boundary is not that clear, and it is true
> that writing a complete pinctrl driver is really overkill.
> I've tried in the past, and gave up due to the complexity of fmwk
> and the lack of time. I still think, it is a much better fmwk to
> handle pin configuration than the regulator fmwk.

For omaps, these kind of registers can already be handled by
pinctrl-single,bits. What's missing is the capability to create
a regulator out of the voltage mux + comparator bits.
 
> >That's pretty much along the lines what Roger has done,
> >except the transceiver could use the pinctrl-single,bits for the
> >muxing and pinconf.
> 
> Well, in that case, this is a reset line, so it does not have
> anything to do with voltage :-)
> 
> Anyway, thanks to Florian, we know that there is a real solution to
> that problem. It is just not merged now :-(

Right. Meanwhile, sounds like the transceiver driver needs to
deal with the GPIO directly.

Regards,

Tony
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