On Fri, 22 Nov 2013, Dan Williams wrote: > Summary: > 1/ Half the size of v1 [1], drop peer port power control for now > 2/ Make port power control more robust by reusing the existing > "reset-resume" implementation for connection recovery. > > First off, this set diverges significantly from the initial RFC [1]. It > frontloads the fixes to the top of the patchset and completely drops the > attempt to track and synchronize peer ports (peer ports being the paired > USB3 and USB2 phys that share a connector). As a result, it is about > half the size of the original set. 5 of the patches cleanup/delete more > lines than they add (patches 1, 3, 4, 7 and 12) and patch 14 updates the > power-management document for port power control. > > At this point it looks as though the peer port power coordination code > may not be necessary. Testing high frequency port power toggling indeed > caused a USB3 SATA bridge device to switch from its USB3 connection to > USB2. However, the same "disconnect" (failure to reconnect on resume) > occurred whether the peer USB2 port was powered or not. The hypothesis > is that upon seeing a high frequency connection toggle the device > eventually gives up on trying to connect via its USB3 phy. Regardless, > the failure mode is not modulated by the power state of the peer port. > > "[PATCH v2 13/14] USB: ratelimit port power transitions" follows that > line of thinking and prevents userspace from toggling power faster than > one recovery (reset-resume) cycle. With patch 13 in place the test > device reliably reconnects via its USB3 connection. We can revisit this > if we encounter devices that aggressively downgrade to USB2; however, > the suspicion is that those devices would have proven to be flakey with > the power session losses that occur during system suspend. > > Patches 1, 6, 7, and 13 are the meat of the implemenation rework. > > Patches 9 - 11 are straightforward and simply take/drop a pm reference > anytime one of the power off constraints is touched. > > Remaining patches are cleanups, minor fixes, and documentation. > > Please review, much appreciated. I want to look through all of this, but it will take a while -- perhaps a week or so. Lots of other stuff going on now... 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
