linux-kernel - Re: [PATCH 1/2] usb: gadget: u_ether: Do not make UDC parent of the net device

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Date:   Thu, 9 Feb 2023 12:41:03 +0100
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     linux-usb@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH 1/2] usb: gadget: u_ether: Do not make UDC parent of the
 net device

On Thu, Feb 09, 2023 at 10:37:05AM +0000, Paul Cercueil wrote:
> Hi Sascha,
> 
> Le jeudi 09 février 2023 à 11:18 +0100, Sascha Hauer a écrit :
> > Hi Paul,
> > 
> > On Wed, Feb 01, 2023 at 01:32:51PM +0000, Paul Cercueil wrote:
> > > Hi Sascha, Greg,
> > > 
> > > I have a breakage in 6.2-rc* that I eventually bisected to this
> > > commit,
> > > on a Ingenic SoC (using the jz4740 musb driver) with ECM or RNDIS
> > > configured through gadgetfs.
> > > 
> > > When plugging the board to my PC, the USB network interface is
> > > recognized, but 'ip link' sees it as 'NO-CARRIER'. With this commit
> > > reverted on v6.2-rc5, everything works fine.
> > 
> > I don't have this hardware available. I just tried with a i.MX
> > hardware
> > and it works as expected. I have no idea where the jz4740 musb could
> > behave differently.
> > 
> > Here's exactly what I did:
> > 
> > mkdir -p /sys/kernel/config/usb_gadget/mygadget
> > cd /sys/kernel/config/usb_gadget/mygadget
> > mkdir -p configs/c.1/strings/0x409
> > echo "C1:Composite Device" > configs/c.1/strings/0x409/configuration
> > mkdir -p functions/ecm.usb0
> > ln -s functions/ecm.usb0 configs/c.1/
> > echo "ci_hdrc.0" > UDC
> > 
> > Did you do something differently apart from the "ci_hdrc.0" of
> > course?
> 
> Nothing very different, no.
> 
> I do:
> 
> cd /sys/kernel/config/usb_gadget
> mkdir mtp \
>   mtp/strings/0x409 \
>   mtp/configs/c.1 \
>   mtp/configs/c.1/strings/0x409 \
>   mtp/functions/ffs.mtp \
>   mtp/functions/ecm.net \
>   mtp/functions/rndis.net
> 
> echo 0x80 > mtp/configs/c.1/bmAttributes
> echo 500 > mtp/configs/c.1/MaxPower
> 
> echo 0x049f > mtp/idVendor
> echo 0x505a > mtp/idProduct
> echo cdc > mtp/configs/c.1/strings/0x409/configuration
> ln -s mtp/functions/ecm.net mtp/configs/c.1/ecm.net
> 
> echo ci_hdrc.0 > mtp/UDC
> 
> > BTW when you say 'NO-CARRIER' is it on the PC side, board side, or
> > both?
> 
> PC side. I don't know what it says on the board side, I can't
> telnet/SSH.

I just checked on the host side: With or without my patch I get
NO-CARRIER on the host. I have to do a 'ip link set usb0 up' on
the device side, with that I get a <BROADCAST,MULTICAST,UP,LOWER_UP>
on the host side.

Could it be that my patch breaks something on the device side that
prevents the device from bringing the link up?

Sascha

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