Re: [PATCH 1/4] xhci: Keep interrupt disabled in initialization until host is running.

[Prashanth K <quic_prashk@quicinc.com>]

On 23-06-22 04:49 pm, Mathias Nyman wrote:
> From: Hongyu Xie <xy521521@gmail.com>
> 
> 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.
> 
> [tidy up old code while moving it, reword header -Mathias]
> Cc: stable@kernel.org
> Signed-off-by: Hongyu Xie <xiehongyu1@kylinos.cn>
> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
> ---
>   drivers/usb/host/xhci.c | 35 ++++++++++++++++++++++-------------
>   1 file changed, 22 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 9ac56e9ffc64..cb99bed5f755 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -611,15 +611,37 @@ static int xhci_init(struct usb_hcd *hcd)
>   
>   static int xhci_run_finished(struct xhci_hcd *xhci)
>   {
> +	unsigned long	flags;
> +	u32		temp;
> +
> +	/*
> +	 * Enable interrupts before starting the host (xhci 4.2 and 5.5.2).
> +	 * Protect the short window before host is running with a lock
> +	 */
> +	spin_lock_irqsave(&xhci->lock, flags);
> +
> +	xhci_dbg_trace(xhci, trace_xhci_dbg_init, "Enable interrupts");
> +	temp = readl(&xhci->op_regs->command);
> +	temp |= (CMD_EIE);
> +	writel(temp, &xhci->op_regs->command);
> +
> +	xhci_dbg_trace(xhci, trace_xhci_dbg_init, "Enable primary interrupter");
> +	temp = readl(&xhci->ir_set->irq_pending);
> +	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 +690,6 @@ 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;
>   
This is not available to older kernels [< 5.19]. Can we get this 
backported to 5.15 as well? Please let me know if there is some other 
way to do it.

Cc: <stable@vger.kernel.org> # 5.15

Thanks,
Prashanth K