linux-kernel - Re: [PATCH] usb: musb: Force-disable pullup on shutdown

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Date:   Wed, 3 Apr 2019 08:26:00 -0500
From:   Bin Liu <b-liu@...com>
To:     Paul Cercueil <paul@...pouillou.net>
CC:     <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <od@...c.me>
Subject: Re: [PATCH] usb: musb: Force-disable pullup on shutdown

On Tue, Apr 02, 2019 at 09:58:42PM +0200, Paul Cercueil wrote:
> Hi,
> 
> Le lun. 1 avril 2019 à 20:20, Bin Liu <b-liu@...com> a écrit :
> >On Mon, Apr 01, 2019 at 07:46:22PM +0200, Paul Cercueil wrote:
> >>
> >>
> >> Le lun. 1 avril 2019 à 19:17, Bin Liu <b-liu@...com> a écrit :
> >> >On Thu, Mar 21, 2019 at 03:42:46PM +0100, Paul Cercueil wrote:
> >> >> When the musb is shutdown, for instance when the driver is
> >>unloaded,
> >> >> force-disable the pullup. Otherwise, the host will still see
> >> >>the gadget
> >> >> device even after the shutdown.
> >> >
> >> >how would this happen?
> >> >
> >> >when musb-hdrc driver is unloaded, udc core removes the bound
> >>gadget
> >> >driver which calls musb_gadget_pullup() to disable the pullup.
> >>
> >> I'm testing with the jz4740-musb driver. I don't unload the
> >>module (it's
> >> built-in) but unbind it from sysfs.
> >
> >I did unbind too.
> >
> >root@...35x-evm:/sys/bus/platform/drivers/musb-hdrc# echo
> >musb-hdrc.0 > unbind
> >
> >or unbind the glue driver:
> >
> >root@...35x-evm:/sys/bus/platform/drivers/musb-dsps# echo
> >47401400.usb > unbind
> >
> >musb_gadget_pullup() is called in both cases.
> >
> >[ 3880.597014] [<bf444ab0>] (musb_gadget_pullup [musb_hdrc]) from
> >[<bf402cbc>] (usb_gadget_disconnect+0x3c/0xf4 [udc_core])
> >[ 3880.607959] [<bf402cbc>] (usb_gadget_disconnect [udc_core])
> >from [<bf403b28>] (usb_gadget_remove_driver+0x4c/0x90 [udc_core])
> >[ 3880.619338] [<bf403b28>] (usb_gadget_remove_driver [udc_core])
> >from [<bf403d20>] (usb_del_gadget_udc+0x5c/0xc0 [udc_core])
> 
> In my case this stops here, usb_del_gadget_udc() does not call
> usb_gadget_remove_driver(), that's why the pullup is never disabled.
> 
> I guess that's because udc->driver is NULL; I'm testing with

then the pullup should be disable by now.

> CONFIG_USB_CONFIGFS,
> and I don't configure anything in sysfs before unbinding the driver.

I didn't check on this, but I could imagine that
- when a configfs gadget is bound to the udc, .pullup() is called;
- when the configfs gadget is unbound from the udc, .pullup should be
  called again to disable the pullup.

-Bin.