On Tue, 23 Apr 2013, Peter Chen wrote: > On Mon, Apr 22, 2013 at 11:26:05AM -0400, Alan Stern wrote: > > On Mon, 22 Apr 2013, Peter Chen wrote: > > > > > Hi all, > > > > > > Recently, I have several customers troubled in safe recover USB > > > function during the ESD situation (or some other situations, like > > > short dp/dm, ground dp/dm, etc). > > > > > > I designed the ESD detect and recovery process, but I met some > > > sync problems between host controller driver (eg, ehci) and class > > > driver (eg, mass storage). For example, when khubd tries to disconnect > > > usb device, it will try to stop thread usb-storage, but usb-storage > > > is waiting some transfers to finish, qTD and QH operation may be > > > finished (usb_submit_urb does not return error), but no watchdog timer > > > and completion interrupt are occurred. > > > > > > I have: > > > esd_detect_process and esd_recovery_process at host controller driver. > > > At esd_detect_porcess > > > It will disable usb interrupt and judge ASE and PSE, etc. > > > At esd_recovery_process: > > > It needs to reset controller (usbcmd.rst, and toggle portsc.pp bit, etc) > > > > > > I would like to have some synchronization mechanism between usb_submit_urb > > > or (ehci_urb_enqueue) and my esd_detect_process and esd_recovery_process. > > > But still not find a safe one, eg, I still met khubd's status changes > > > "D" problem described above. Any suggestions are appreciated, Thanks. > > > > Your recovery process should not need to make all these changes to > > ehci-hcd. Simply carry out the same actions as the "dead:" statement > > label in ehci_irq() -- that is, do the same thing as if an interrupt > > occurred with the STS_FATAL bit set. That code is all properly > > synchronized. > > Sometimes, there are no STS_FATAL and STA_ERR when ESD occurs. > So, you suggest do the same thing for STS_FATAL at my esd_recovery_process? Yes. > > Then unbind the driver from the controller and rebind it. Rebinding > > will reset the controller. > > > > You mean unbind the controller driver? Any existed API can be called? > I can't do rmmod at that time. You can call device_release_driver, after locking both the controller's parent and the controller itself. See driver_unbind() in drivers/base/bus.c. Or, if you are doing this in userspace, you can write the controllers device name to /sys/bus/.../drivers/.../unbind. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
