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

[Paul Cercueil]

Le mer. 3 avril 2019 à 15:26, Bin Liu <b-liu@xxxxxx> 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@xxxxxx> 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@xxxxxx> 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@am335x-evm:/sys/bus/platform/drivers/musb-hdrc# echo
> >  >musb-hdrc.0 > unbind
> >  >
> >  >or unbind the glue driver:
> >  >
> >  >root@am335x-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
configfs gadget is never bound, then .pullup() is never called, and when
I unbind the driver the pullup is still enabled.

-Paul