USB: xhci: Reduce reads and writes of interrupter registers. (c21599a3) · Commits · 戴 / test

The interrupter register set includes a register that says whether interrupts are pending for each event ring (the IP bit). Each MSI-X vector will get its own interrupter set with separate IP bits. The status register includes an "Event Interrupt (EINT)" bit that is set when an IP bit is set in any of the interrupters. When PCI interrupts are used, the EINT bit exactly mirrors the IP bit in the single interrupter set, and it is a waste of time to check both registers when trying to figure out if the xHC interrupted or another device on the shared IRQ line interrupted. Only check the IP bit to reduce register reads. The IP bit is automatically cleared by the xHC when MSI or MSI-X is enabled. It doesn't make sense to read that register to check for shared interrupts (since MSI and MSI-X aren't shared). It also doesn't make sense to write to that register to clear the IP bit, since it is cleared by the hardware. We can tell whether MSI or MSI-X is enabled by looking at the irq number in hcd->irq. If it's -1, we know MSI or MSI-X is enabled. Signed-off-by:

Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by:

Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/xhci-ring.c

+10 −8

Original line number	Diff line number	Diff line
		@@ -2014,7 +2014,7 @@ static void xhci_handle_event(struct xhci_hcd *xhci)
		irqreturn_t xhci_irq(struct usb_hcd *hcd)
		{
		struct xhci_hcd *xhci = hcd_to_xhci(hcd);
		u32 status, irq_pending;
		u32 status;
		union xhci_trb *trb;
		u64 temp_64;
		union xhci_trb *event_ring_deq;
		@@ -2024,17 +2024,15 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd)
		trb = xhci->event_ring->dequeue;
		/* Check if the xHC generated the interrupt, or the irq is shared */
		status = xhci_readl(xhci, &xhci->op_regs->status);
		irq_pending = xhci_readl(xhci, &xhci->ir_set->irq_pending);
		if (status == 0xffffffff && irq_pending == 0xffffffff)
		if (status == 0xffffffff)
		goto hw_died;

		if (!(status & STS_EINT) && !ER_IRQ_PENDING(irq_pending)) {
		if (!(status & STS_EINT)) {
		spin_unlock(&xhci->lock);
		xhci_warn(xhci, "Spurious interrupt.\n");
		return IRQ_NONE;
		}
		xhci_dbg(xhci, "op reg status = %08x\n", status);
		xhci_dbg(xhci, "ir set irq_pending = %08x\n", irq_pending);
		xhci_dbg(xhci, "Event ring dequeue ptr:\n");
		xhci_dbg(xhci, "@%llx %08x %08x %08x %08x\n",
		(unsigned long long)
		@@ -2063,9 +2061,13 @@ hw_died:
		/* FIXME when MSI-X is supported and there are multiple vectors */
		/* Clear the MSI-X event interrupt status */

		/* Acknowledge the interrupt */
		if (hcd->irq != -1) {
		u32 irq_pending;
		/* Acknowledge the PCI interrupt */
		irq_pending = xhci_readl(xhci, &xhci->ir_set->irq_pending);
		irq_pending \|= 0x3;
		xhci_writel(xhci, irq_pending, &xhci->ir_set->irq_pending);
		}

		if (xhci->xhc_state & XHCI_STATE_DYING) {
		xhci_dbg(xhci, "xHCI dying, ignoring interrupt. "

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