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 11:19:31 -0500
From:	Bin Liu <b-liu@...com>
To:	David Lechner <david@...hnology.com>
CC:	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>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	<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

Hi,

On Fri, Apr 01, 2016 at 11:02:23AM -0500, David Lechner wrote:
> On 04/01/2016 09:45 AM, 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. 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.

Regards,
-Bin.