linux-kernel - Re: [PATCH v3 04/10] usb: dwc3: use quirks to know if a particualr platform doesn't have PHY

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Message-ID: <52A82B44.10408@ti.com>
Date:	Wed, 11 Dec 2013 14:37:16 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>, <balbi@...com>
CC:	<bcousson@...libre.com>, <devicetree@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-usb@...r.kernel.org>, <rob.herring@...xeda.com>,
	<pawel.moll@....com>, <mark.rutland@....com>,
	<swarren@...dotorg.org>, <ijc+devicetree@...lion.org.uk>,
	<rob@...dley.net>, <tony@...mide.com>, <linux@....linux.org.uk>,
	<gregkh@...uxfoundation.org>, <grant.likely@...aro.org>,
	<s.nawrocki@...sung.com>, <galak@...eaurora.org>
Subject: Re: [PATCH v3 04/10] usb: dwc3: use quirks to know if a particualr
 platform doesn't have PHY

On Wednesday 11 December 2013 02:23 PM, Heikki Krogerus wrote:
> Hi,
> 
> On Mon, Dec 09, 2013 at 11:26:04AM +0200, Heikki Krogerus wrote:
>>>>>> Can you guys explain why is something like this needed? Like with
>>>>>> clocks and gpios, the device drivers shouldn't need to care any more
>>>>>> if the platform has the phys or not. -ENODEV tells you your platform
>>>>>
>>>>> Shouldn't we report if a particular platform needs a PHY and not able to get
>>>>> it. How will a user know if a particular controller is not working because it's
>>>>> not able to get and initialize the PHYs? Don't you think in such cases it's
>>>>> better to fail (and return from probe) because the controller will not work
>>>>> anyway without the PHY?
>>>>
>>>> My point is that you do not need to separately tell this to the driver
>>>> like you do with the quirks (if you did, then you would need to fix
>>>> your framework and not hack the drivers).
>>>>
>>>> Like I said, ENODEV tells you that there is no phy on this platform
>>>> for you, allowing you to safely continue. If your phy driver is not
>>>> loaded, the framework already returns EPROBE_DEFER, right. Any other
>>>
>>> right. but that doesn't consider broken dt data. With quirks we'll
>>> able to tell if a controller in a particular platform has PHY or not
>>> without depending on the dt data.
>>
>> Broken dt data? What kind of scenario are you thinking here? Do you
>> mean case where the dt does not describe the phy on a platform that
>> depends on it? Shouldn't that problem be fixed in the dt and not
>> hacked in the drivers? Or are you thinking about something else?
>>
>> Is there a case where something like that is actually happening?
> 
> I'm guessing I'm not getting an answer to this one.
> 
> Look, this patch will not work with ACPI enumerated devices. We will
> have a platform providing a single ACPI id, but there is a whole bunch
> of boards based on it and we have no way of telling which of them
> need/have phys to deal with and which ones don't.

Alright.. I'll drop this patch then.

Thanks
Kishon
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