[U-Boot] [PATCH v2 0/4] usb: Reduce USB scanning time

[Stefan Roese]

My current x86 platform (Bay Trail, not in mainline yet) has a quite
complex USB infrastructure with many USB hubs. Here the USB scan takes
an incredible huge amount of time:

starting USB...
USB0:   USB EHCI 1.00
scanning bus 0 for devices... 9 USB Device(s) found

time: 28.415 seconds

This is of course not acceptable on platforms, where USB needs to get
scanned at every bootup. As this increases the bootup time of this
device by nearly 30 seconds!

This patch series greatly reduces the USB scanning time. This is done
by multiple means:

- Remove or reduce delays and timeouts
- Remove a 2nd reset of the USB hubs
- Change USB port timeout handling and introduce quasi parallel USB
  port scanning

As a result, the USB scanning time is greatly reduced:

starting USB...
USB0:   USB EHCI 1.00
scanning bus 0 for devices... 9 USB Device(s) found

time: 4.606 seconds

As you can see, the time is reduced from 28.4 to 4.6 seconds!

Please find more details to the changes in the patch description.

Testing and comments welcome!

Thanks,
Stefan

Changes in v2:
- Add Acked-by / Tested-by from Hans and Stephen
- Make this change unconditional
- Add Acked-by / Tested-by from Hans and Stephen
- Make this change unconditional
- Add Tested-by from Stephen
- Remove static USB port configuration patch (for now)

Stefan Roese (4):
  usb: legacy_hub_port_reset(): Speedup hub reset handling
  usb: Remove 200 ms delay in usb_hub_port_connect_change()
  usb: Don't reset the USB hub a 2nd time
  usb: Change power-on / scanning timeout handling

 common/usb.c     |  13 +------
 common/usb_hub.c | 110 +++++++++++++++++++++++++++++++++++++++----------------
 include/usb.h    |   2 +
 3 files changed, 81 insertions(+), 44 deletions(-)

-- 
2.7.3