On Wed, 20 Feb 2008, David Brownell wrote:
> ========= CUT HERE
> Modify EHCI irq handling on the theory that at least some of the
> "lost" IRQs are caused by goofage between multiple lowlevel IRQ
> acking mechanisms: try rescanning before we exit the handler, in
> case the EHCI-internal ack (by clearing the irq status) doesn't
> always suffice for IRQs triggered nearly back-to-back.
>
> ---
> drivers/usb/host/ehci-hcd.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> --- g26.orig/drivers/usb/host/ehci-hcd.c 2008-02-20 13:26:00.000000000
> -0800
> +++ g26/drivers/usb/host/ehci-hcd.c 2008-02-20 13:54:37.000000000 -0800
> @@ -638,6 +638,8 @@ static irqreturn_t ehci_irq (struct usb_
> return IRQ_NONE;
> }
>
> +retrigger:
> +
> /* clear (just) interrupts */
> ehci_writel(ehci, status, &ehci->regs->status);
> cmd = ehci_readl(ehci, &ehci->regs->command);
> @@ -725,6 +727,12 @@ dead:
>
> if (bh)
> ehci_work (ehci);
> +
> + status = ehci_readl(ehci, &ehci->regs->status);
> + status &= INTR_MASK;
> + if (status)
> + goto retrigger;
> +
> spin_unlock (&ehci->lock);
> if (pcd_status & STS_PCD)
> usb_hcd_poll_rh_status(hcd);
There's one little problem here. As a result of this change, the line
where pcd_status gets set (not shown in this patch) needs to be changed
to:
pcd_status |= (status & STS_PCD);
Then the test shown above can be simplified to:
if (pcd_status)
Alan Stern
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