[U-Boot] [PATCH 1/3] usb: ci_udc: Fix set address to work with older controllers

[Stephen Warren]

On 02/24/2015 09:44 AM, Alban Bedel wrote:
> Older controllers don't implement "Device Address Advance" which allow
> to pass the device address to the controller when it is received.
> To support such controller we need to store the requested address and
> only apply it after the next IN transfer completed on EP0.

> diff --git a/drivers/usb/gadget/ci_udc.c b/drivers/usb/gadget/ci_udc.c

>   	case SETUP(USB_RECIP_DEVICE, USB_REQ_SET_ADDRESS):
> -		/*
> -		 * write address delayed (will take effect
> -		 * after the next IN txn)
> -		 */
> -		writel((r.wValue << 25) | (1 << 24), &udc->devaddr);
> +		/* The device address must be updated after the next IN
> +		 * request completed */
> +		controller.set_address = r.wValue;

Presumably, bit 24 is the "device address advance" feature?

I'd prefer it if new controllers used the existing code, but we deferred 
the write only for older controllers that don't support "device address 
advance". That reduces the possibility of regressions on controller HW 
that's already working. Presumably, there is some advantage using the 
new feature, rather than deferring the address change manually, e.g. it 
solves some race condition?