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: 1.822 seconds
As you can see, the time is reduced from 28.4 to 1.8 seconds!
Please find more details to the changes in the patch description.
Testing and comments welcome!
Thanks, Stefan
Changes in v3: - Changed small timeout from 10ms to 20ms as this results in a much faster USB scanning time (10ms too small and 20ms enough in many cases) - Introduced scanning list containing all USB devices of one USB controller that need to get scanned - Don't delay in usb_hub_power_on(). Instead skip querying these devices until the delay time is reached.
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 | 301 +++++++++++++++++++++++++++++++++++++------------------ include/usb.h | 3 + 3 files changed, 208 insertions(+), 109 deletions(-)