On Tue, 2012-01-10 at 10:25 -0500, Alan Stern wrote:
> On Tue, 10 Jan 2012, Alex,Shi wrote:
>
> >
> > We have a PCI USB xhci host controller on a new platform. It have no
> > line IRQ definition in BIOS. So the Linux driver refuses to initial this
> > controller. But Windows works well for it depending on MSI.
> >
> > Actually, Linux also can work for MSI. This patch skips the first line
> > IRQ checking for our HCD in usb-core pci probe, then try to enable MSI
> > firstly. That make this HCD works well under Linux.
> >
> > Thanks for Sarah's suggestion and review for this patch.
>
> > diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> > index 13222d3..6545454 100644
> > --- a/drivers/usb/core/hcd.c
> > +++ b/drivers/usb/core/hcd.c
> > @@ -2466,8 +2466,11 @@ int usb_add_hcd(struct usb_hcd *hcd,
> > && device_can_wakeup(&hcd->self.root_hub->dev))
> > dev_dbg(hcd->self.controller, "supports USB remote wakeup\n");
> >
> > - /* enable irqs just before we start the controller */
> > - if (usb_hcd_is_primary_hcd(hcd)) {
> > + /* enable irqs just before we start the controller. But xhci primary
> > + * hcd doesn't need this, since it will do it in driver->start();
>
> There's no need to mention xhci in this comment, since the reasoning is
> valid no matter what type of controller you have.
Yes, will rewrite the comments
>
> > + */
> > + if (usb_hcd_is_primary_hcd(hcd) &&
> > + !(hcd->driver->flags & HCD_MSI_FST)) {
> > retval = usb_hcd_request_irqs(hcd, irqnum, irqflags);
> > if (retval)
> > goto err_request_irq;
>
> What happens here if HCD_MSI_FIRST is set in the driver but the
> controller uses regular IRQs instead of MSI? You'll skip calling
> usb_hcd_request_irqs, and the driver won't work.
following driver->start() will call xhci_try_enable_msi(), so, it is
still have chance to fall back line irq.
>
> Alan Stern
>
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