Hi Alan,
On 10/26/2021 7:41 AM, Alan Stern wrote:
> On Mon, Oct 25, 2021 at 05:44:56PM -0700, Wesley Cheng wrote:
>> From: Wesley Cheng <wcheng@xxxxxxxxxxxxxx>
>>
>> When receiving a disconnect event from the UDC, the mass storage
>> function driver currently runs the handle_exception() routine
>> asynchronously. For UDCs that support runtime PM, there is a
>> possibility the UDC is already suspended by the time the
>> do_set_interface() is executed. This can lead to HW register access
>> while the UDC is already suspended.
>>
>> Signed-off-by: Wesley Cheng <wcheng@xxxxxxxxxxxxxx>
>> ---
>> drivers/usb/gadget/function/f_mass_storage.c | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c
>> index 3cabf7692ee1..752439690fda 100644
>> --- a/drivers/usb/gadget/function/f_mass_storage.c
>> +++ b/drivers/usb/gadget/function/f_mass_storage.c
>> @@ -2342,6 +2342,16 @@ static void fsg_disable(struct usb_function *f)
>> {
>> struct fsg_dev *fsg = fsg_from_func(f);
>>
>> + /* Disable the endpoints */
>> + if (fsg->bulk_in_enabled) {
>> + usb_ep_disable(fsg->bulk_in);
>
> According to the kerneldoc, this routine must be called in process
> context.
>
>> + fsg->bulk_in_enabled = 0;
>> + }
>> + if (fsg->bulk_out_enabled) {
>> + usb_ep_disable(fsg->bulk_out);
>> + fsg->bulk_out_enabled = 0;
>> + }
>> +
>> __raise_exception(fsg->common, FSG_STATE_CONFIG_CHANGE, NULL);
>> }
>
> Looks like you'll have to find a different way to avoid the problem.
> For example, if an exception is pending then you might prevent the
> gadget from going into runtime suspend until the exception has been
> handled.
>
Thanks for the suggestion. I noticed that a lot of other FDs currently
call usb_ep_disable() in the disable/disconnect path as well. Actually,
f_mass_storage seems to be the only one that doesn't do so. Maybe we
should change the kerneldoc :)
Thanks
Wesley Cheng
