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

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Message-ID: <51C1A2AE.2020506@ti.com>
Date:	Wed, 19 Jun 2013 07:23:10 -0500
From:	Benoit Cousson <b-cousson@...com>
To:	<florian.vaussard@...l.ch>, Roger Quadros <rogerq@...com>
CC:	<devicetree-discuss@...ts.ozlabs.org>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 1/4] ARM: dts: omap4-panda: Add USB Host support

On 06/19/2013 07:05 AM, Florian Vaussard wrote:
> Hello,
>
> On 06/19/2013 01:03 PM, Roger Quadros wrote:
>> On 06/19/2013 01:10 PM, Benoit Cousson wrote:
>>> On 06/19/2013 02:46 AM, Tony Lindgren wrote:
>>>> * Roger Quadros <rogerq@...com> [130619 00:42]:
>>>>> Hi Benoit,
>>>>>
>>>>> On 06/19/2013 04:17 AM, Benoit Cousson wrote:
>>>>>> Hi Roger,
>>>>>>
>>>>>> On 06/18/2013 11:04 AM, Roger Quadros wrote:
>>>>>>> Provide the RESET and Power regulators for the USB PHY,
>>>>>>> the USB Host port mode and the PHY device.
>>>>>>>
>>>>>>> Also provide pin multiplexer information for the USB host
>>>>>>> pins.
>>>>>>>
>>>>>>> Signed-off-by: Roger Quadros <rogerq@...com>
>>>>>>> ---
>>>>>>>     arch/arm/boot/dts/omap4-panda-common.dtsi |   62
>>>>>>> +++++++++++++++++++++++++++++
>>>>>>>     1 files changed, 62 insertions(+), 0 deletions(-)
>>>>>>>
>>>>>>> diff --git a/arch/arm/boot/dts/omap4-panda-common.dtsi
>>>>>>> b/arch/arm/boot/dts/omap4-panda-common.dtsi
>>>>>>> index 00cbaa5..7a21e8e 100644
>>>>>>> --- a/arch/arm/boot/dts/omap4-panda-common.dtsi
>>>>>>> +++ b/arch/arm/boot/dts/omap4-panda-common.dtsi
>>>>>>> @@ -59,6 +59,42 @@
>>>>>>>                 "AFML", "Line In",
>>>>>>>                 "AFMR", "Line In";
>>>>>>>         };
>>>>>>> +
>>>>>>> +    /* HS USB Port 1 RESET */
>>>>>>> +    hsusb1_reset: hsusb1_reset_reg {
>>>>>>> +        compatible = "regulator-fixed";
>>>>>>> +        regulator-name = "hsusb1_reset";
>>>>>>> +        regulator-min-microvolt = <3300000>;
>>>>>>> +        regulator-max-microvolt = <3300000>;
>>>>>>> +        gpio = <&gpio2 30 0>;    /* gpio_62 */
>>>>>>> +        startup-delay-us = <70000>;
>>>>>>> +        enable-active-high;
>>>>>>> +    };
>>>>>>
>>>>>> Is this really a regulator? Or just a GPIO line used to reset the
>>>>>> USB PHY?
>>>>>
>>>>> It is in fact a GPIO line used as reset.
>>>>>>
>>>>>> If this is the case, I don't think it should be represented as a
>>>>>> regulator.
>>>>>
>>>>> Why not? I think it fits very well in the regulator device model.
>>>
>>> I'm not sure fitting very well is the correct term.
>>> It works, for sure, but it is no different than when we were trying
>>> to abuse the regulator fmwk to enable the 32k clock in phoenix.
>>> It is just a hack.
>>>
>>
>> The only difference is there is a dedicated framework for clocks.
>> Since there is nothing specific to
>> handle reset lines it is left to the driver writer how he wants to
>> manage it.
>>
>
> There is a proposed binding for gpio-controlled reset lines, but it is
> not yet merged [1].
> I guess it can fit most usage patterns, and it can be an interesting
> move in the future.

I'm glad to see that I was not the only one thinking that the regulator 
was not the right fmwk to do that :-)

Thanks for the pointer Florian.

I guess that series should be merged for 3.11? Based on the thread, it 
should to through arm-soc.

Roger,

It might be tricky to have dependency on that series, but if this is 
possible, you should try. Otherwise, just keep the existing one, adding 
that a new solution will be available soon as a disclaimer.

Regards,
Benoit

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