[U-Boot] [PATCH v5 4/4] usb: Change power-on / scanning timeout handling

[Stephen Warren]

On 03/15/2016 06:59 AM, Stefan Roese wrote:
> This patch changes the USB port scanning procedure and timeout
> handling in the following ways:
>
> a)
> The power-on delay in usb_hub_power_on() is now reduced to a value of
> max(100ms, "hub->desc.bPwrOn2PwrGood * 2"). The code does not wait
> using mdelay, instead usb_hub_power_on() will wait before querying
> the device in the scanning loop later. The total timeout for this
> hub, which is 1 second + "hub->desc.bPwrOn2PwrGood * 2" is calculated
> and will be used in the following per-port scanning loop as the timeout
> to detect active USB devices on this hub.
>
> b)
> Don't delay the minimum delay (for power to stabilize) in
> usb_hub_power_on(). Instead skip querying these devices in the scannig
> loop until the delay time is reached.
>
> c)
> The ports are now scanned in a quasi parallel way. The current code did
> wait for each (unconnected) port to reach its timeout and only then
> continue with the next port. This patch now changes this to scan all
> ports of all USB hubs quasi simultaneously. For this, all ports are added
> to a scanning list. This list is scanned until all ports are ready
> by either a) reaching the connection timeout (calculated earlier), or
> by b) detecting a USB device. This results in a faster USB scan time as
> the recursive scanning of USB hubs connected to the hub that's currently
> being scanned will start earlier.
>
> One small functional change to the original code is, that ports with
> overcurrent detection will now get rescanned multiple times
> (PORT_OVERCURRENT_MAX_SCAN_COUNT).
>
> Without this patch:
> starting USB...
> USB0:   USB EHCI 1.00
> scanning bus 0 for devices... 9 USB Device(s) found
>
> time: 20.163 seconds
>
> With this patch:
> starting USB...
> USB0:   USB EHCI 1.00
> scanning bus 0 for devices... 9 USB Device(s) found
>
> time: 1.822 seconds
>
> So ~18.3 seconds of USB scanning time reduction.
>
> Signed-off-by: Stefan Roese <sr at denx.de>
> Acked-by: Hans de Goede <hdegoede at redhat.com>
> Tested-by: Stephen Warren <swarren at nvidia.com>

This version still works for me (the timing numbers I sent a few minutes 
ago were with this version too).