linux-kernel - Re: [PATCH] usb: Make sure usb/phy/of gets built-in

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Date:   Tue, 18 Apr 2017 12:23:20 +0000
From:   Alexey Brodkin <Alexey.Brodkin@...opsys.com>
To:     "frowand.list@...il.com" <frowand.list@...il.com>
CC:     "jk@...abs.org" <jk@...abs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "nbd@....name" <nbd@....name>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "nicolas.pitre@...aro.org" <nicolas.pitre@...aro.org>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "yamada.masahiro@...ionext.com" <yamada.masahiro@...ionext.com>,
        "geert+renesas@...der.be" <geert+renesas@...der.be>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] usb: Make sure usb/phy/of gets built-in

Hello Frank,

On Mon, 2017-04-17 at 20:15 -0700, Frank Rowand wrote:
> On 04/13/17 05:33, Alexey Brodkin wrote:
> > 
> > DWC3 driver uses of_usb_get_phy_mode() which is
> > implemented in drivers/usb/phy/of.c and in bare minimal
> > configuration it might not be pulled in kernel binary.
> > 
> > In case of ARC or ARM this could be easily reproduced with
> > "allnodefconfig" +CONFIG_USB=m +CONFIG_USB_DWC3=m.
> > 
> > On building all ends-up with:
> > ---------------------->8------------------
> >   Kernel: arch/arm/boot/Image is ready
> >   Kernel: arch/arm/boot/zImage is ready
> >   Building modules, stage 2.
> >   MODPOST 5 modules
> > ERROR: "of_usb_get_phy_mode" [drivers/usb/dwc3/dwc3.ko] undefined!
> > make[1]: *** [__modpost] Error 1
> > make: *** [modules] Error 2
> > ---------------------->8------------------
> > 
> > Signed-off-by: Alexey Brodkin <abrodkin@...opsys.com>
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
> > Cc: Geert Uytterhoeven <geert+renesas@...der.be>
> > Cc: Nicolas Pitre <nicolas.pitre@...aro.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Felipe Balbi <balbi@...nel.org>
> > Cc: Felix Fietkau <nbd@....name>
> > Cc: Jeremy Kerr <jk@...abs.org>
> > Cc: linux-snps-arc@...ts.infradead.org
> > Cc: stable@...r.kernel.org
> > ---
> >  drivers/Makefile | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/Makefile b/drivers/Makefile
> > index 2eced9afba53..8f8bdc9e3d29 100644
> > --- a/drivers/Makefile
> > +++ b/drivers/Makefile
> > @@ -104,6 +104,7 @@ obj-$(CONFIG_USB_PHY)		+= usb/
> >  obj-$(CONFIG_USB)		+= usb/
> >  obj-$(CONFIG_PCI)		+= usb/
> >  obj-$(CONFIG_USB_GADGET)	+= usb/
> 
> > 
> > +obj-$(CONFIG_OF)		+= usb/
> 
> Would CONFIG_USB_SUPPORT make more sense? (And does it work?)

Well I'm not really sure here.

The problem was in missing "drivers/usb/phy/of.o" in "drivers/usb/built-in.o".
So I took a look at how components get enabled and saw quite mixed stuff.

In "drivers/usb/phy/Makefile" we see:
------------------------->8---------------------------
obj-$(CONFIG_OF)»       »       »       += of.o
------------------------->8---------------------------

In "drivers/usb/Makefile" we see:
------------------------->8---------------------------
obj-$(CONFIG_USB_SUPPORT)»      += phy/
------------------------->8---------------------------

From above I may conclude that your proposal should work as well
but it's more a question of which approach is safer and more future proof.

Maybe it even worth adding the following to "drivers/usb/Makefile":
------------------------->8---------------------------
obj-$(CONFIG_USB_SUPPORT)»      += phy/
------------------------->8---------------------------

Any thoughts are more than welcome.

-Alexey