[PATCH] usb: ehci: make HC see up-to-date qh/qtd descriptor ASAP

just another measurement point

Stephen Warren wrote at Thursday:

Here are the results I found:

Harmony:
Tegra USB3 -> SMSC9514 hub: NOT affected
(Unplugging LAN cable, or disabling SMSC9514 LAN driver doesn't change
this)

Seaboard (springbank; clamshell):
Tegra USB1 -> no hub: Affected

Seaboard (seaboard non-clamshell):
Tegra USB1 -> no hub: Affected
Tegra USB3 -> no hub: Affected

TrimSlice:
Tegra USB3 -> unknown hub: Affected

PAZ00:
ULPI -> SMCS 2512: Affected
Tegra USB3 -> SMSC 2514: Affected

The patch also cures high latencies/packet drops on wifi connected to ULPI via 
the 2512 hub. The pen drive was connected to USB3/2514.

This implies there's something different about Harmony.

Is the USB hub a clue? Seaboard doesn't have one, and although I don't
know what model TrimSlice uses, I assume it's different since I know
TrimSlice's Ethernet is not the same as Harmony's.

I don't see anything in board-harmony.c vs. board-seaboard.c that'd affect
anything USB-related.

Perhaps there's some kind of bootloader or BCT difference. However, my
Harmony and both Seaboards both use (a very old) U-Boot and BCT from
ChromeOS, so I don't imagine there's actually much difference there.