[U-Boot] [PATCH v5 0/4] usb: Reduce USB scanning time

[Bin Meng]

Hi Stefan,

On Tue, Mar 15, 2016 at 8:59 PM, Stefan Roese <sr at denx.de> wrote:
>
> 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
>

This is a great improvement. Thanks!

Some numbers FYI.

I've tested the v5 patch on Intel Crown Bay. The 'usb start' command
takes about 3 seconds to finish, compared to previously 9 seconds.

Regards,
Bin