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

[Bin Meng]

On Tue, Mar 15, 2016 at 8:59 PM, Stefan Roese <sr at denx.de> 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>
>
> ---
>
> Changes in v5:
> - Removed superfluous debug output from usb_scan_port()
> - Replaced usb_hub_power_on() with usb_set_port_feature() in case
>   of overcurrent detection. This is whats really needed here.
> - Added a per-port overcurrent counter and stop re-scanning of
>   a device that exceeds the PORT_OVERCURRENT_MAX_SCAN_COUNT
> - Moved list_del() to end of loop in usb_scan_port()
> - Moved timeout / delay variables from USB dev to hub struct
>   as they are hub specific
> - Moved state_get_skip_delays() to usb_hub_power_on() so that
>   the timeouts are not set there
>
> Changes in v4:
> - Moved check for query_delay into usb_scan_port() as suggested by Hans
> - Correct list handling (drop INIT_LIST_HEAD)
> - Added some missing free() calls
> - Changed connect_timeout calculation as suggested by Stephen
> - Moved usb_scan_list to other globals to be cleaned up in a later patch
> - Added timeout check for non-functional ports (usb_get_port_status
>   return error
> - Reverted if logic in loop to remove an indentation level
> - Moved debug() output
> - Removed unnecessary if when already connected
> - Added Hans's Acked-by
> - Added Stephen's Tested-by
> - Minor rewording / fixes of the commit text
>
> Changes in v3:
> - 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:
> - Remove static USB port configuration patch (for now)
>
>  common/usb_hub.c | 317 ++++++++++++++++++++++++++++++++++++++-----------------
>  include/usb.h    |   4 +
>  2 files changed, 227 insertions(+), 94 deletions(-)
>

Tested-by: Bin Meng <bmeng.cn at gmail.com>