linux-kernel - Re: [PATCH v2 06/11] phy: da8xx-usb: new driver for DA8XX SoC USB PHY

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Date:	Fri, 1 Apr 2016 22:49:25 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Bin Liu <b-liu@...com>, David Lechner <david@...hnology.com>,
	Kishon Vijay Abraham I <kishon@...com>,
	Petr Kulhavy <petr@...ix.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Sekhar Nori <nsekhar@...com>,
	Kevin Hilman <khilman@...nel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andreas Färber <afaerber@...e.de>,
	Tony Lindgren <tony@...mide.com>,
	Robert Jarzmik <robert.jarzmik@...e.fr>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v2 06/11] phy: da8xx-usb: new driver for DA8XX SoC USB PHY

On 04/01/2016 07:19 PM, Bin Liu wrote:

>>>>> +EXPORT_SYMBOL_GPL(da8xx_usb20_phy_set_mode);
>>>>
>>>> Don't prefer export symbols from PHY driver. That'll create unnecessary
>>>> dependencies between the controller and the PHY.
>>>
>>> Agreed.
>>>
>>>>
>>>> I think it'll be better to create a new attribute and use it?
>>>
>>> Another simpler option is to not support _set_mode() for DA8xx, and the
>>> phy driver set the otgmode bit in probe() based on dr_mode of the
>>> controller.
>>>
>>> Regards,
>>> -Bin.
>>>
>>
>> This certainly works for my particular use case, however, Sergei
>> Shtylyov, who wrote the da8xx musb glue layer originally, seemed to
>> recall in his review of the patch series that this really is
>> necessary for OTG mode to work properly.
>
> I don't know much about the usb module on DA8xx, but it seems to me that
> _set_mode() has nothing to do with OTG mode.

    No, it does.

> musb_core only calls
> _set_mode() in two places - 1) sysfs: musb_mode_store(), 2) init:
> musb_init_controller(). None of them should be related to OTG mode.

    Both these places do select OTG mode.

> Regards,
> -Bin.

MBR, Sergei