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

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Message-ID: <20190403185423.GS25852@uda0271908>
Date:   Wed, 3 Apr 2019 13:54:23 -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 Wed, Apr 03, 2019 at 05:52:20PM +0200, Paul Cercueil wrote:
> 
> 
> Le mer. 3 avril 2019 à 17:46, Bin Liu <b-liu@...com> a écrit :
> >On Wed, Apr 03, 2019 at 05:31:31PM +0200, Paul Cercueil wrote:
> >>
> >>
> >> Le mer. 3 avril 2019 à 15:26, Bin Liu <b-liu@...com> a écrit :
> >> >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.
> >>
> >> An important thing that I did not mention, is that the SoC boots
> >> from USB,
> >> so the pullup is active before the musb driver loads. Since in
> >>my case a
> >
> >It sounds to me that the musb driver should disable the pullup during
> >init.  Isn't it?
> 
> Yes. I can move it to musb_gadget_setup(). Should I still protect it
> with
> the spinlock then?

Thanks. I don't think spinlock is necessary here.

-Bin.