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

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Message-Id: <1554235122.13181.0@crapouillou.net>
Date:   Tue, 02 Apr 2019 21:58:42 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Bin Liu <b-liu@...com>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, od@...c.me
Subject: Re: [PATCH] usb: musb: Force-disable pullup on shutdown

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

> [ 3880.630471] [<bf403d20>] (usb_del_gadget_udc [udc_core]) from 
> [<bf439ff8>] (musb_remove+0x50/0x134 [musb_hdrc])
> [ 3880.640648] [<bf439ff8>] (musb_remove [musb_hdrc]) from 
> [<c05668cc>] (platform_drv_remove+0x28/0x48)
> [ 3880.649831] [<c05668cc>] (platform_drv_remove) from [<c0564e3c>] 
> (device_release_driver_internal+0xe4/0x1b4)
> [ 3880.659708] [<c0564e3c>] (device_release_driver_internal) from 
> [<c05633e4>] (bus_remove_device+0xe0/0x140)
> [ 3880.669409] [<c05633e4>] (bus_remove_device) from [<c055f358>] 
> (device_del+0x140/0x374)
> [ 3880.677455] [<c055f358>] (device_del) from [<c0566ff0>] 
> (platform_device_del.part.3+0x18/0x80)
> [ 3880.686110] [<c0566ff0>] (platform_device_del.part.3) from 
> [<c0567098>] (platform_device_unregister+0x24/0x30)
> [ 3880.696170] [<c0567098>] (platform_device_unregister) from 
> [<bf48c3e0>] (dsps_remove+0x1c/0x38 [musb_dsps])
> [ 3880.706010] [<bf48c3e0>] (dsps_remove [musb_dsps]) from 
> [<c05668cc>] (platform_drv_remove+0x28/0x48)
> [ 3880.715190] [<c05668cc>] (platform_drv_remove) from [<c0564e3c>] 
> (device_release_driver_internal+0xe4/0x1b4)
> [ 3880.725065] [<c0564e3c>] (device_release_driver_internal) from 
> [<c0562b2c>] (unbind_store+0x64/0xd8)
> [ 3880.734253] [<c0562b2c>] (unbind_store) from [<c0350c58>] 
> (kernfs_fop_write+0xf4/0x1cc)
> 
> Regards,
> -Bin.
> 
>