Re: [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