Subject: Re: [PATCH v2 06/11] phy: da8xx-usb: new driver for DA8XX SoC USB PHY
To: Bin Liu <b-liu@ti.com>, David Lechner <david@lechnology.com>,
        Kishon Vijay Abraham I <kishon@ti.com>, Petr Kulhavy <petr@barix.com>,
        Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Ian Campbell <ijc+devicetree@hellion.org.uk>,
        Kumar Gala <galak@codeaurora.org>,
        Russell King <linux@arm.linux.org.uk>, Sekhar Nori <nsekhar@ti.com>,
        Kevin Hilman <khilman@kernel.org>,
        Alan Stern <stern@rowland.harvard.edu>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        =?UTF-8?Q?Andreas_F=c3=a4rber?= <afaerber@suse.de>,
        Tony Lindgren <tony@atomide.com>,
        Robert Jarzmik <robert.jarzmik@free.fr>, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-usb@vger.kernel.org
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 <56FE74AC.6080303@ti.com> <20160401144510.GA6264@uda0271908>
 <56FE9B8F.7050605@lechnology.com> <20160401161931.GC6264@uda0271908>
From: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Organization: Cogent Embedded
Message-ID: <56FED0C5.1000603@cogentembedded.com>
Date: Fri, 1 Apr 2016 22:49:25 +0300
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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