[U-Boot] [PATCH 5/7] usb: Assure Get Descriptor request is in separate microframe

[Stephen Warren <swarren@wwwdotorg.org>]

On 05/03/2016 02:51 PM, Marek Vasut wrote:
> The Kingston DT Ultimate USB 3.0 stick is sensitive to this first
> Get Descriptor request and if the request is not in a separate
> microframe, the stick refuses to operate. Add slight delay, which
> is enough for one microframe to pass on any USB spec revision.

> diff --git a/common/usb.c b/common/usb.c

> +	/*
> +	 * Kingston DT Ultimate 32GB USB 3.0 seems to be extremely sensitive
> +	 * about this first Get Descriptor request. If there are any other
> +	 * requests in the first microframe, the stick crashes. Wait about
> +	 * one microframe duration here (1mS for USB 1.x , 125uS for USB 2.0).
> +	 */
> +	mdelay(1);

Do we know the connection speed here? If so, we could sleep 1ms for 
USB1.x and 125us for USB2.x, thus reducing any performance impact. 
Still, this is a short delay that I think only happens once per actual 
device so perhaps it isn't worth it.