New: Suspending to mem hangs the machine without the BT driver loaded

https://bugzilla.kernel.org/show_bug.cgi?id=199125

            Bug ID: 199125
           Summary: Suspending to mem hangs the machine without the BT
                    driver loaded
           Product: Drivers
           Version: 2.5
    Kernel Version: 4.16.0-rc5
          Hardware: x86-64
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Bluetooth
          Assignee: [email protected]
          Reporter: [email protected]
        Regression: No

On an Intel GLK NUC machine suspending to memory (S3) hangs if the BT driver is not enabled. Specifically the following kconfig options need to be enabled to avoid the hang:

CONFIG_BT
CONFIG_BT_INTEL
CONFIG_BT_HCIBTUSB

An alternative is to disable the Bluetooth onboard device in BIOS.

The hang happens after execution transfers to BIOS code during suspend, after the very last ACPI register write to entry S3 in drivers/acpi/acpica/hwsleep.c:

after the following call in acpi_hw_legacy_sleep():
/* Write #2: Write both SLP_TYP + SLP_EN */

        status = acpi_hw_write_pm1_control(pm1a_control, pm1b_control); 

In general not loading the BT driver may be a useful thing to work-around potential BT driver bugs, or during isolation of a bug without a known reason (by unloading drivers one-by-one and seeing if the problem re-occurs).

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