xhci crash at xhci_disable_hub_port_wake when system suspend.

[Frank Li <frank.li@nxp.com>]

Mathias Nyman

	Recently we found a crash at xhci_disable_hub_port_wake when system suspend if enable remote wake up.

	Basial flow is.

	1. run time suspend call xhci_suspend, xhci parent devices gate the clock. 
	2. echo mem >/sys/power/state, system _device_suspend call xhci_suspend
	3. xhci_suspend call xhci_disable_hub_port_wake, which access register, but clock already gated by run time pm. 

	Why find this issue now, that is because previous power domain driver will call run time resume before it. But the below commit remove it. 

c1df456d0f06eb9275c1cd4c66548fc5738ea428
Author: Ulf Hansson ulf.hansson@linaro.org
Date:   Thu Mar 4 20:28:43 2021 +0100

    PM: domains: Don't runtime resume devices at genpd_prepare()


	
According to HCD_FLAG_HW_ACCESSIBLE logic, xhci should not access hardware when second time call xhci_suspend without call xhci_resume. 

        xhci_disable_hub_port_wake(xhci, &xhci->usb3_rhub, do_wakeup);
        xhci_disable_hub_port_wake(xhci, &xhci->usb2_rhub, do_wakeup);

        if (!HCD_HW_ACCESSIBLE(hcd))
                return 0;

        .....
        clear_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
        clear_bit(HCD_FLAG_HW_ACCESSIBLE, &xhci->shared_hcd->flags);

I am not sure if it is safe to move xhci_disable_hub_port_wake after HCD_HW_ACCESSIBLE check, Or need add additional run_time_resume before it. 


best regards
Frank Li