[U-Boot] [PATCH 5/6] usb: Don't reset the USB hub a 2nd time

Hans de Goede
2016-03-10T19:13:25Z

Hi,

On 10-03-16 16:50, Stefan Roese wrote:
> Debugging has shown, that all USB hubs are being resetted twice while
> USB scanning. This introduces additional delays and makes USB scanning
> even more slow. Testing has shown that this 2nd USB hub reset doesn't
> seem to be necessary.
>
> This patch now removes this 2nd USB hub reset if CONFIG_USB_FAST_SCAN
> is defined. Resulting in faster USB scan time. Here the current
> number:
>
> Without this patch:
> => time usb start
> starting USB...
> USB0: USB EHCI 1.00
> scanning bus 0 for devices... 9 USB Device(s) found
>
> time: 6.319 seconds
>
> With this patch:
> => time usb start
> starting USB...
> USB0: USB EHCI 1.00
> scanning bus 0 for devices... 9 USB Device(s) found
>
> time: 3.777 seconds
>
> So ~2.5 seconds of USB scanning time reduction.
>
> Again, this 2nd reset is only removed if CONFIG_USB_FAST_SCAN is
> defined. Once more tests are done on multiple other platforms we
> can decide to remove this 2nd reset completely.

I see no reason to make the removal conditional, I believe that
this is some relic workaround for likely long fixed bugs and
we should just remove it completely (for v2016.07).

Regards,

Hans

>
> Signed-off-by: Stefan Roese <sr@denx.de>
> Cc: Simon Glass <sjg@chromium.org>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: Stephen Warren <swarren@nvidia.com>
> Cc: Marek Vasut <marex@denx.de>
> ---
>
> common/usb.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/common/usb.c b/common/usb.c
> index c7b8b0e..b96a2f6 100644
> --- a/common/usb.c
> +++ b/common/usb.c
> @@ -920,6 +920,11 @@ __weak int usb_alloc_device(struct usb_device *udev)
> static int usb_hub_port_reset(struct usb_device *dev, struct usb_device *hub)
> {
> if (hub) {
> +#if !defined(CONFIG_USB_FAST_SCAN)
> + /*
> + * Is this 2nd hub port reset necessary? The port has already
> + * been reset in usb_hub_port_connect_change() before.
> + */
> unsigned short portstatus;
> int err;
>
> @@ -929,6 +934,7 @@ static int usb_hub_port_reset(struct usb_device *dev, struct usb_device *hub)
> printf("\n Couldn't reset port %i\n", dev->portnr);
> return err;
> }
> +#endif
> } else {
> usb_reset_root_port(dev);
> }
>