[U-Boot] Regression due to 020bbcb "usb: hub: Power-cycle on root-hub ports"

[Stephen Warren]

(Sorry to those on to/cc; I'm resending this so it goes to the correct
mailing list)

Commit 020bbcb "usb: hub: Power-cycle on root-hub ports" causes a
regression on Tegra systems.

The first time "usb start" is executed, it appears to work correctly.
However, any subsequent time it is executed, it takes a long time, and
eventually fails to find any USB devices.

This situation can happen quite often; for example, if the user forgets
to plug in a USB device before booting, runs "usb start", realizes that,
then plugs it in and runs "usb start" again. This is compounded on at
least one of the Tegra boards, since CONFIG_PREBOOT is set to "usb
start" on systems (laptops/clamshells) which have built-in USB keyboards.

If I simply revert this patch, then everything works again. (Yes,
reverting requires fixing a small merge conflict.)

Do you have any idea what the problem can be? I'm tempted to simply ask
for the patch to be reverted since it causes a regression.

Thanks for any idea how to fix this!