[PATCH v2 -next] usb: xhci: disable irq during initialization

[PATCH v2 -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@kylinos.cn>
---

v2: fix compile error

 drivers/usb/host/xhci.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 9ac56e9ffc64..513bcd346886 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -611,6 +611,7 @@ static int xhci_init(struct usb_hcd *hcd)
 
 static int xhci_run_finished(struct xhci_hcd *xhci)
 {
+	u32 temp;
 	if (xhci_start(xhci)) {
 		xhci_halt(xhci);
 		return -ENODEV;
@@ -620,6 +621,19 @@ static int xhci_run_finished(struct xhci_hcd *xhci)
 	if (xhci->quirks & XHCI_NEC_HOST)
 		xhci_ring_cmd_db(xhci);
 
+	/* 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);
 	return 0;
 }
 
@@ -668,19 +682,6 @@ 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

Re: [PATCH v2 -next] usb: xhci: disable irq during initialization

[Mathias Nyman]

On 15.6.2022 12.07, Hongyu Xie wrote:
> 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
I see, makes sense to enable interrupts as close as possible to where we
start the host.

For some unknown reason xHCI specification recommends enabling interrupts
(INTE and IE bits) before setting the Run/Stop bit, see xhci 4.2
Host Controller Initialization, "Note" part

So the order here needs to be swapped to comply with spec.
This unfortunately also creates a small window where xHC can interrupt
before xHC is running, but it's better than current situation.

This small window could be solved by protecting this part with a
spin_lock_irqsave().

Thanks
-Mathias