linux-kernel - Re: [PATCH 01/15] drivers: phy: add generic PHY framework

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Message-ID: <51E8DE51.1060404@ti.com>
Date:	Fri, 19 Jul 2013 12:06:01 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	<kyungmin.park@...sung.com>, <balbi@...com>, <jg1.han@...sung.com>,
	<s.nawrocki@...sung.com>, <kgene.kim@...sung.com>,
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	<swarren@...dia.com>, <devicetree-discuss@...ts.ozlabs.org>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
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	<linux-usb@...r.kernel.org>, <linux-media@...r.kernel.org>,
	<linux-fbdev@...r.kernel.org>, <akpm@...ux-foundation.org>,
	<balajitk@...com>, <george.cherian@...com>, <nsekhar@...com>
Subject: Re: [PATCH 01/15] drivers: phy: add generic PHY framework

Hi,

On Friday 19 July 2013 11:59 AM, Greg KH wrote:
> On Fri, Jul 19, 2013 at 11:25:44AM +0530, Kishon Vijay Abraham I wrote:
>> Hi,
>>
>> On Friday 19 July 2013 11:13 AM, Greg KH wrote:
>>> On Fri, Jul 19, 2013 at 11:07:10AM +0530, Kishon Vijay Abraham I wrote:
>>>>>>>> +	ret = dev_set_name(&phy->dev, "%s.%d", dev_name(dev), id);
>>>>>>>
>>>>>>> Your naming is odd, no "phy" anywhere in it?  You rely on the sender to
>>>>>>> never send a duplicate name.id pair?  Why not create your own ids based
>>>>>>> on the number of phys in the system, like almost all other classes and
>>>>>>> subsystems do?
>>>>>>
>>>>>> hmm.. some PHY drivers use the id they provide to perform some of their
>>>>>> internal operation as in [1] (This is used only if a single PHY provider
>>>>>> implements multiple PHYS). Probably I'll add an option like PLATFORM_DEVID_AUTO
>>>>>> to give the PHY drivers an option to use auto id.
>>>>>>
>>>>>> [1] ->
>>>>>> http://archive.arm.linux.org.uk/lurker/message/20130628.134308.4a8f7668.ca.html
>>>>>
>>>>> No, who cares about the id?  No one outside of the phy core ever should,
>>>>> because you pass back the only pointer that they really do care about,
>>>>> if they need to do anything with the device.  Use that, and then you can
>>>>
>>>> hmm.. ok.
>>>>
>>>>> rip out all of the "search for a phy by a string" logic, as that's not
>>>>
>>>> Actually this is needed for non-dt boot case. In the case of dt boot, we use a
>>>> phandle by which the controller can get a reference to the phy. But in the case
>>>> of non-dt boot, the controller can get a reference to the phy only by label.
>>>
>>> I don't understand.  They registered the phy, and got back a pointer to
>>> it.  Why can't they save it in their local structure to use it again
>>> later if needed?  They should never have to "ask" for the device, as the
>>
>> One is a *PHY provider* driver which is a driver for some PHY device. This will
>> use phy_create to create the phy.
>> The other is a *PHY consumer* driver which might be any controller driver (can
>> be USB/SATA/PCIE). The PHY consumer will use phy_get to get a reference to the
>> phy (by *phandle* in the case of dt boot and *label* in the case of non-dt boot).
>>> device id might be unknown if there are multiple devices in the system.
>>
>> I agree with you on the device id part. That need not be known to the PHY driver.
> 
> How does a consumer know which "label" to use in a non-dt system if
> there are multiple PHYs in the system?

That should be passed using platform data.
> 
> Do you have any drivers that are non-dt using this yet?

yes. tw4030 (used in OMAP3) supports non-dt.
[PATCH 04/15] ARM: OMAP: USB: Add phy binding information
[PATCH 06/15] usb: musb: omap2430: use the new generic PHY framework
of this patch series shows how it's used.

Thanks
Kishon
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