On Fri, 2 Nov 2012, Miguel Dardenne wrote: > Hello all, > > > First, apologies if this message is not posted to the right mailing > list - please point me to the most appropriate one if needed. > > I get a USB disconnect of my external USB HDD about once per day. > Enabling USB debug in the kernel shows the first error as 'ehci_hcd > detected XactErr'. It happens only when the drive is idle. For example, > I had a process writing on the HDD every 3 seconds and the problem did > not occur for several weeks. Correction: These errors do not occur when the drive is idle. You can see in the log you attached: > [170639.102539] ehci_hcd 0000:00:0f.5: detected XactErr len 2048/4096 > retry 1 This means that a 4096-byte data transfer was in progress and an error occurred after 2048 bytes had been sent. This is a low-level hardware type of error (the computer did not get an acknowledgement when sending data). It is not a software error. > The bad thing is that it reconnects on another device - initialy > /dev/sdb, it becomes /dev/sdc, which of course breaks quite a few > things. > > Changing the USB cable did nothing and the disk works fine on other > computers (Windows-based). I thus suspect a power management bug. No. The drive remains at full power as long as it is mounted. If the power level were changed, it would show up in your debugging log. > Before resorting to disabling power management altogether, I would like > some advice/insights on what is going on here, and would like to help > solve this issue with the best efforts I can provide. It appears that the drive disconnected itself from the USB bus. There's no indication of why this happened. 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
