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

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Message-ID: <51C1A55E.9040500@ti.com>
Date:	Wed, 19 Jun 2013 07:34:38 -0500
From:	Benoit Cousson <b-cousson@...com>
To:	Tony Lindgren <tony@...mide.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

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.

> 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 :-(

Regards,
Benoit
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