On Fri, 8 Apr 2011, Alan Stern wrote:
> On Thu, 7 Apr 2011, Greg KH wrote:
>
> > Here's Thomas's first cut at doing this, totally untested and written
> > during a legal track at the LF Collab summit.
> >
> > Kristen, can you take this and test and see if it works for you?
> >
> > thanks,
> >
> > greg k-h
> >
> >
> > Subject: usb.patch
> > From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Date: Thu, 07 Apr 2011 23:35:16 +0200
> >
> > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > ---
> > drivers/usb/core/hcd.c | 42 ++++++++++++++++++++----------------------
> > drivers/usb/host/ehci-hcd.c | 33 +++++++++++++++++++++++++++------
> > drivers/usb/host/ehci-pci.c | 1 +
> > include/linux/usb/hcd.h | 1 +
> > 4 files changed, 49 insertions(+), 28 deletions(-)
>
> This isn't correct, for a couple of reasons. The most important reason
> shows up here:
>
> > Index: linux-2.6/drivers/usb/host/ehci-hcd.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/usb/host/ehci-hcd.c
> > +++ linux-2.6/drivers/usb/host/ehci-hcd.c
> > @@ -764,10 +764,35 @@ static int ehci_run (struct usb_hcd *hcd
> > static irqreturn_t ehci_irq (struct usb_hcd *hcd)
> > {
> > struct ehci_hcd *ehci = hcd_to_ehci (hcd);
> > + u32 status;
> > +
> > + spin_lock(&ehci->lock);
> > +
> > + status = ehci_readl(ehci, &ehci->regs->status);
> > + if (status & INTR_MASK)
> > + ehci_writel(ehci, 0, &ehci->regs->intr_enable);
> > +
> > + spin_unlock(&ehci->lock);
> > +
> > + return status & INTR_MASK ? IRQ_WAKE_THREAD : IRQ_NONE;
> > +}
>
> The status information gets thrown away. It has to be saved for later
> use.
Whoops, I spoke too soon. The information doesn't get thrown away.
Forget I mentioned it.
On the other hand, the interrupts need to be re-enabled somewhere. I
didn't notice that anywhere in the patch.
Also, the patch assumes that ehci_threaded_irq will be called only in
response to interrupt events. That isn't (or at least, it isn't
supposed to be) true. There are places where usb_hcd_irq() is invoked
directly from other code.
Alan Stern
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