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

Alban Bedel
2015-02-24T17:41:22Z

On Tue, 24 Feb 2015 10:00:43 -0700
Stephen Warren <swarren@wwwdotorg.org> wrote:

> 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?

Yes, 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?

I'm no USB expert, but AFAIU it is only a convenience to make the
driver code simpler. I though that having less code path and ifdef
would make the whole thing easier to maintain. However if that is
preferred I can implement it as you suggested.

Alban

PS: Sorry for the double mail Stephen, I accidentally used the wrong
reply button.
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