[U-Boot] [PATCH 2/6] usb: Remove 200 ms delay in usb_hub_port_connect_change()

Hans de Goede
2016-03-10T18:55:34Z

Hi,

On 10-03-16 16:50, Stefan Roese wrote:
> This patch removes 2 mdelay(200) calls from usb_hub_port_connect_change().
> These delays don't seem to be necessary. At least not in my tests. Here
> the number for a custom x86 Bay Trail board (not in mainline yet) with
> a quite large and complex USB hub infrastructure.
>
> Without this patch:
> starting USB...
> USB0: USB EHCI 1.00
> scanning bus 0 for devices... 9 USB Device(s) found
>
> time: 28.415 seconds
>
> With this patch:
> starting USB...
> USB0: USB EHCI 1.00
> scanning bus 0 for devices... 9 USB Device(s) found
>
> time: 24.811 seconds
>
> So ~3.5 seconds of USB scanning time reduction.
>
> These mdelay calls are removed if CONFIG_USB_FAST_SCAN is defined. They
> are not removed per default yet. It would be good to test with this
> option enabled on many other boards. And once we have a good testing
> base we can decide to remove these delays completely, including this
> macro.

There indeed is no reason at all to delay before the reset and the kernel
does not wait with checking the USB_PORT_STAT_SPEED_MASK once the
reset completes, so I see no reason why we should:

Acked-by: Hans de Goede <hdegoede@redhat.com>

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_hub.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/common/usb_hub.c b/common/usb_hub.c
> index 10fdd3c..660f4f4 100644
> --- a/common/usb_hub.c
> +++ b/common/usb_hub.c
> @@ -275,7 +275,9 @@ int usb_hub_port_connect_change(struct usb_device *dev, int port)
> if (!(portstatus & USB_PORT_STAT_CONNECTION))
> return -ENOTCONN;
> }
> +#if !defined(CONFIG_USB_FAST_SCAN)
> mdelay(200);
> +#endif
>
> /* Reset the port */
> ret = legacy_hub_port_reset(dev, port, &portstatus);
> @@ -285,7 +287,9 @@ int usb_hub_port_connect_change(struct usb_device *dev, int port)
> return ret;
> }
>
> +#if !defined(CONFIG_USB_FAST_SCAN)
> mdelay(200);
> +#endif
>
> switch (portstatus & USB_PORT_STAT_SPEED_MASK) {
> case USB_PORT_STAT_SUPER_SPEED:
>