Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability

From: Peter Zijlstra
Date: Wed Jan 25 2017 - 09:38:40 EST

On Wed, Jan 25, 2017 at 08:27:38PM +0800, Lu Baolu wrote:
> In my driver, udelay() is mostly used to handle time out.
> Xdbc hides most USB things in its firmware. Early printk driver only needs
> to setup the registers/data structures and wait until link ready or time out.
> Without udelay(), I have no means to convert the polling times into waiting
> time.

What is timeout and why? If there is an error other than !ready, I would
expect the hardware to inform you of this through another status bit,

So why can't you poll indefinitely for either ready or error?