USB: xhci: Remove unnecessary reads of IRQ_PENDING register.

Remove a duplicate register read of the interrupt pending register from
xhci_irq().  Also, remove waiting on the posted write of that register.
The host will see it eventually.  It will probably read the register
itself before deciding whether to interrupt the system again, forcing the
posted write to complete.
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

@@ -2039,25 +2039,25 @@ 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 temp, temp2;
+	u32 status, irq_pending;
 	union xhci_trb *trb;
 	u64 temp_64;
 
 	spin_lock(&xhci->lock);
 	trb = xhci->event_ring->dequeue;
 	/* Check if the xHC generated the interrupt, or the irq is shared */
-	temp = xhci_readl(xhci, &xhci->op_regs->status);
-	temp2 = xhci_readl(xhci, &xhci->ir_set->irq_pending);
-	if (temp == 0xffffffff && temp2 == 0xffffffff)
+	status = xhci_readl(xhci, &xhci->op_regs->status);
+	irq_pending = xhci_readl(xhci, &xhci->ir_set->irq_pending);
+	if (status == 0xffffffff && irq_pending == 0xffffffff)
 		goto hw_died;
 
-	if (!(temp & STS_EINT) && !ER_IRQ_PENDING(temp2)) {
+	if (!(status & STS_EINT) && !ER_IRQ_PENDING(irq_pending)) {
 		spin_unlock(&xhci->lock);
 		xhci_warn(xhci, "Spurious interrupt.\n");
 		return IRQ_NONE;
 	}
-	xhci_dbg(xhci, "op reg status = %08x\n", temp);
-	xhci_dbg(xhci, "ir set irq_pending = %08x\n", temp2);
+	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)
@@ -2067,7 +2067,7 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd)
 			(unsigned int) trb->link.intr_target,
 			(unsigned int) trb->link.control);
 
-	if (temp & STS_FATAL) {
+	if (status & STS_FATAL) {
 		xhci_warn(xhci, "WARNING: Host System Error\n");
 		xhci_halt(xhci);
 hw_died:
@@ -2081,15 +2081,14 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd)
 	 * so we can receive interrupts from other MSI-X interrupters.
 	 * Write 1 to clear the interrupt status.
 	 */
-	temp |= STS_EINT;
-	xhci_writel(xhci, temp, &xhci->op_regs->status);
+	status |= STS_EINT;
+	xhci_writel(xhci, status, &xhci->op_regs->status);
 	/* FIXME when MSI-X is supported and there are multiple vectors */
 	/* Clear the MSI-X event interrupt status */
 
 	/* Acknowledge the interrupt */
-	temp = xhci_readl(xhci, &xhci->ir_set->irq_pending);
-	temp |= 0x3;
-	xhci_writel(xhci, temp, &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. "
@@ -2103,8 +2102,6 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd)
 	/* Clear the event handler busy flag (RW1C); event ring is empty. */
 	temp_64 = xhci_read_64(xhci, &xhci->ir_set->erst_dequeue);
 	xhci_write_64(xhci, temp_64 | ERST_EHB, &xhci->ir_set->erst_dequeue);
-	/* Flush posted writes -- FIXME is this necessary? */
-	xhci_readl(xhci, &xhci->ir_set->irq_pending);
 	spin_unlock(&xhci->lock);
 
 	return IRQ_HANDLED;