[PATCH v4 -next] usb: xhci: disable irq during initialization

[Hongyu Xie]

irq is disabled in xhci_quiesce(called by xhci_halt, with bit:2 cleared
in USBCMD register), but xhci_run(called by usb_add_hcd) re-enable it.
It's possible that you will receive thousands of interrupt requests
after initialization for 2.0 roothub. And you will get a lot of
warning like, "xHCI dying, ignoring interrupt. Shouldn't IRQs be
disabled?". This amount of interrupt requests will cause the entire
system to freeze.
This problem was first found on a device with ASM2142 host controller
on it.

Signed-off-by: Hongyu Xie <xiehongyu1@xxxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
---

v4: add definition for flags
v3:
- enabling interrupt right before setting Run/Stop bit
- spin_lock_irqsave to prevent receiving irqs in the small window
according to Mathias's suggestion
v2: fix compile error

 drivers/usb/host/xhci.c | 41 +++++++++++++++++++++++++++--------------
 1 file changed, 27 insertions(+), 14 deletions(-)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 9ac56e9ffc64..1344cc566338 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -611,15 +611,41 @@ static int xhci_init(struct usb_hcd *hcd)
 
 static int xhci_run_finished(struct xhci_hcd *xhci)
 {
+	unsigned long flags;
+	u32 temp;
+
+	/* Prevent receiving irqs in the small window between enabling interrupt
+	 * and setting Run/Stop bit
+	 */
+	spin_lock_irqsave(&xhci->lock, flags);
+
+	/* Enable interrupt right before setting Run/Stop bit according to spec
+	 * 4.2
+	 */
+	/* Set the HCD state before we enable the irqs */
+	temp = readl(&xhci->op_regs->command);
+	temp |= (CMD_EIE);
+	xhci_dbg_trace(xhci, trace_xhci_dbg_init,
+			"// Enable interrupts, cmd = 0x%x.", temp);
+	writel(temp, &xhci->op_regs->command);
+
+	temp = readl(&xhci->ir_set->irq_pending);
+	xhci_dbg_trace(xhci, trace_xhci_dbg_init,
+			"// %s %p by writing 0x%x %s",
+			"Enabling event ring interrupter",
+			"to irq_pending", xhci->ir_set,
+			(unsigned int) ER_IRQ_ENABLE(temp));
+	writel(ER_IRQ_ENABLE(temp), &xhci->ir_set->irq_pending);
 	if (xhci_start(xhci)) {
 		xhci_halt(xhci);
+		spin_unlock_irqrestore(&xhci->lock, flags);
 		return -ENODEV;
 	}
 	xhci->cmd_ring_state = CMD_RING_STATE_RUNNING;
 
 	if (xhci->quirks & XHCI_NEC_HOST)
 		xhci_ring_cmd_db(xhci);
-
+	spin_unlock_irqrestore(&xhci->lock, flags);
 	return 0;
 }
 
@@ -668,19 +694,6 @@ int xhci_run(struct usb_hcd *hcd)
 	temp |= (xhci->imod_interval / 250) & ER_IRQ_INTERVAL_MASK;
 	writel(temp, &xhci->ir_set->irq_control);
 
-	/* Set the HCD state before we enable the irqs */
-	temp = readl(&xhci->op_regs->command);
-	temp |= (CMD_EIE);
-	xhci_dbg_trace(xhci, trace_xhci_dbg_init,
-			"// Enable interrupts, cmd = 0x%x.", temp);
-	writel(temp, &xhci->op_regs->command);
-
-	temp = readl(&xhci->ir_set->irq_pending);
-	xhci_dbg_trace(xhci, trace_xhci_dbg_init,
-			"// Enabling event ring interrupter %p by writing 0x%x to irq_pending",
-			xhci->ir_set, (unsigned int) ER_IRQ_ENABLE(temp));
-	writel(ER_IRQ_ENABLE(temp), &xhci->ir_set->irq_pending);
-
 	if (xhci->quirks & XHCI_NEC_HOST) {
 		struct xhci_command *command;
 
-- 
2.25.1