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Date:	Wed, 18 Jun 2014 23:02:30 -0500
From:	Felipe Balbi <balbi@...com>
To:	Nishanth Menon <nm@...com>
CC:	<balbi@...com>, <devicetree@...r.kernel.org>,
	<linux@....linux.org.uk>, Benoit Cousson <bcousson@...libre.com>,
	Tony Lindgren <tony@...mide.com>,
	Rajendra Nayak <rnayak@...com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Darren Etheridge <detheridge@...com>, <r.sricharan@...com>,
	<robh+dt@...nel.org>, Josh Elliot <jelliott@...com>,
	<galak@...eaurora.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Linux ARM Kernel Mailing List 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 2/2] arm: dts: add support for AM437x StarterKit

Hi,

On Wed, Jun 18, 2014 at 10:17:34PM -0500, Nishanth Menon wrote:
> On 06/18/2014 10:05 PM, Felipe Balbi wrote:
> > Hi,
> > 
> > On Wed, Jun 18, 2014 at 09:26:01PM -0500, Nishanth Menon wrote:
> >> On 06/18/2014 06:19 PM, Felipe Balbi wrote:
> >> [...]
> >>>>>>> Add support for TI's AM437x StarterKit Evaluation
> >>>>>>> Module.
> >>>>>>
> >>>>>> is there a link for this platform?
> >>>>>
> >>>>> internal only
> >>>>
> >>>> but will eventually be sold externally? I assume this is not an TI
> >>>
> >>> probably, but there's nothing public yet.
> >>>
> >>>> internal only board.
> >>>
> >>> correct assumption for all I know.
> >>
> >> Yikes.. ok.. I'd let Tony et.al make the call on this, I guess.
> > 
> > would we really block a DTS just because there's no public wiki page
> > available (yet) ?
> > 
> > Sounds a bit extreme to me.
> 
> If this is an TI internal board without anyone outside that a few
> select developers being able to get and work on it... I am a bit
> skeptical on upstream kernel support and burden for forseeable future
> in ensuring it is tested and continually maintained. if it an
> one-off.. maybe fork might be good enough.. upstream not too attractive.

dude, this is a Starter Kit after all. The probability of being sold
eventually is really, really high. I just can't confirm it certainly
will right now.

> I mean, if it is targeted to be sold eventually, I have no objections
> or blocks - just make it clear in commit message. I can imagine folks
> wondering what the heck this is and googling without results(just like
> I did).

I'll point you to schematics and internal wiki tomorrow if you want. I'm
sure there will be a public ti.com address for it though.

> [...]
> 
> >>>>>>> +	cd-gpios = <&gpio0 6 GPIO_ACTIVE_HIGH>;
> >>>>>>> +};
> >>>>>>> +
> >>>>>>> +&usb2_phy1 {
> >>>>>>> +	status = "okay";
> >>>>>>> +};
> >>>>>>> +
> >>>>>>> +&usb1 {
> >>>>>>> +	dr_mode = "peripheral";
> >>>>>>> +	status = "okay";
> >>>>>>> +};
> >>>>>>> +
> >>>>>>> +&usb2_phy2 {
> >>>>>>> +	status = "okay";
> >>>>>>> +};
> >>>>>>> +
> >>>>>>> +&usb2 {
> >>>>>>> +	dr_mode = "host";
> >>>>>>> +	status = "okay";
> >>>>>>> +};
> >>>>>> none of the above need pinctrl? no regulator supplies?
> >>>>>
> >>>>> pins in default states, drivers don't use regulators.
> >>>>
> >>>> USB works without a supply? even a fixed voltage supply? that is
> >>>> weird.
> >>>
> >>> take a look at the minicom output I posted if you don't believe. Well,
> >>> to be exact, tps63010 [1] is the one which generates the regulated V5_0D
> >>> which is used as VBUS_USB. The enable pin in that device is tied to the
> >>> 3v3 rail (dcdc4 regulator in the PMIC as most everything else) but
> >>> there's no way (otherwise) to control that thing. There's no control
> >>> bus, no way to write a driver.
> >>>
> >>> Since the board will anyways turn off if you disable the 3v3 rail, it's
> >>> pretty much pointless to figure out a hack just to add this to DTS.
> >>>
> >>> [1] http://www.ti.com/product/TPS63010
> >>
> >> I am sure to trust you on the test log :) ->  but then from dts description
> >> perspective, it is good if we describe the supplies, even as a always on
> >> fixed-regulator. We had instances like 2430SDP ethernet where... umm... we
> >> originally missed describing ethernet supply and boom, one fine morning, no
> >> more nfs filesystem - I mean, it is a one off scenario there, but describing
> >> regulators helps us atleast understand the power tree of the board a little
> >> better.
> >>
> >> Again, no strong opinions on my side, it is a good thing to do is all
> >> I feel about it.
> > 
> > you mean something like:
> > 
> > 	V5_0D: fixedregulator@0 {
> > 		compatible = "regulator-fixed";
> > 		regulator-name = "V5_0D";
> > 		regulator-min-microvolt = <5000000>;
> > 		regulator-max-microvolt = <5000000>;
> > 		regulator-boot-on;
> > 		regulator-always-on;
> > 		vin-supply = <&dcdc4>;
> > 	};
> > 
> > 	VBUS_USB: fixedregulator@1 {
> > 		compatible = "regulator-fixed";
> > 		regulator-name = "VBUS_USB";
> > 		regulator-min-microvolt = <5000000>;
> > 		regulator-max-microvolt = <5000000>;
> > 		regulator-boot-on;
> > 		regulator-always-on;
> > 		vin-supply = <&V5_0D>;
> > 	};
> > 
> > I can add that, but note that it's *solely* to make sysfs look nice. And
> > if that's the case, most likely *every* DTS file in tree today as
> > incomplete. OTOH, I really consider this to be hugely unnecessary
> > because of the fact that board will turn off if 3v3 (dcdc4) is disabled.
> > 
> 
> 
> Yes - something along those lines - Again, no strong opinions on my
> side for these - just that it is a good thing to model in and may help
> drivers where can use the awareness.

if you ask me, it's just two extra instances of the fixed regulator
driver for a really marginal added benefit.

-- 
balbi

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