[SeaBIOS] [PATCH] [wip] add xhci support

[Kevin O'Connor]

On Mon, Jun 24, 2013 at 11:49:22AM +0200, Gerd Hoffmann wrote:
> Very first revision doing something useful.  Initializes xhci host
> controller, detects devices, can handle control and bulk transfers.
> Good enougth to boot from usb storage devices and handle keyboard.
> 
> Tested on qemu.
> 
> To be done:
>   * Test on real hardware.
>   * Add support for streams (needed for uas devices on usb3 ports).

This is great!

I haven't had a chance to fully review, but I did have a couple of
questions.

[...]
> +static void wait_fixed(u32 timeout)
> +{
> +    u64 end = calc_future_tsc(timeout);
> +
> +    while (!check_tsc(end))
> +        yield();
> +}

How does this differ from msleep()?

[...]
> +struct usb_pipe *
> +xhci_alloc_pipe(struct usbdevice_s *usbdev
> +                , struct usb_endpoint_descriptor *epdesc)
> +{
> +    ASSERT32FLAT();
> +    if (!CONFIG_USB_XHCI)
> +        return NULL;
> +    u8 eptype = epdesc->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK;
> +    struct usb_xhci_s *xhci = container_of(
> +        usbdev->hub->cntl, struct usb_xhci_s, usb);
> +    struct xhci_pipe *pipe;
> +    u32 epid;
> +
> +    if (epdesc->bEndpointAddress == 0) {
> +        epid = 1;
> +    } else {
> +        epid = (epdesc->bEndpointAddress & 0x0f) * 2;
> +        epid += (epdesc->bEndpointAddress & USB_DIR_IN) ? 1 : 0;
> +    }
> +
> +#if 1
> +    /* dirty hack time: try to dig our pipe out of the freelist */
> +    struct usb_pipe **pfree = &xhci->usb.freelist;
> +    for (;;) {
> +        struct usb_pipe *upipe = *pfree;

Can you explain this further.  What's needed to reuse a previously
opened pipe on xhci?

-Kevin