On Mon, Oct 01, 2012 at 01:32:08PM -0400, Alan Stern wrote: > On Mon, 1 Oct 2012, Sarah Sharp wrote: > > Second, I'm wondering if LPM is interacting with system suspend and > > resume in a bad way. I noticed in my log with the USB 3.0 hub and hard > > drive that LPM was disabled for the hub before the system went into > > suspend, but LPM was not disabled for the hard drive. We should have > > disabled LPM if usb_port_suspend() was called for the hard drive's port. > > I'll have to add some more debugging to see if it was called, but I > > don't think it is. > > > > ISTR that you said when the system is suspended or hibernated, only the > > roothub ports are placed into suspend, because the rest of the bus will > > be placed into global suspend when the system goes into S3/S4. > > I said that only the root hub's ports _need_ to be suspended. And of > course, that statement doesn't apply to USB-3 ports. > > > However, > > there is no link state transition between U1/U2 into U3. If a USB 3.0 > > device in the second tier of the tree is in U1/U2 when the system is > > suspended, we're attempting to put it into U3 from U1 or U2. That could > > possibly cause us to hit bugs in the device firmware, since we're > > forcing the device through an undefined link state transition. > > I don't remember the details. Doesn't usb_unlocked_disable_lpm() force > the device back into U0? You call that routine before suspending the > port. It sends the control transfer to bring the port from U1/U2 into U0 and disables any further device or hub initiated U1/U2 transitions. But it doesn't actually _wait_ for the port to enter U0. > > Is my recollection of the system suspend procedure correct, or do I have > > something wrong here? > > Currently we do suspend all the attached devices when going into system > suspend. Hmm, I'll have to do some further debugging, because that probably means there's a bug in the LPM code if the hard drive didn't have LPM disabled before suspend. > But we don't when going into the FREEZE or PRETHAW stages of > hibernation -- all we do is call the bus_suspend routines for root > hubs. That may need to be changed for USB-3 buses. I think so. Where is the code that only calls bus_suspend? I'll take a stab at fixing it. Sarah Sharp -- 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
