On Fri, Nov 22, 2013 at 2:12 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > 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... > Not a problem, this is 3.14 material. Appreciate the heads up. -- Dan -- 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
