cpuidle: Check the result of cpuidle_get_driver() against NULL

If the current CPU has no cpuidle driver, drv will be NULL in
cpuidle_driver_ref().  Check if that is the case before trying
to bump up the driver's refcount to prevent the kernel from
crashing.

[rjw: Subject and changelog]
Signed-off-by: Daniel Fu <danifu@nvidia.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
ACPI / scan: Change ordering of locks for device hotplug

Change the ordering of device hotplug locks in scan.c so that
acpi_scan_lock is always acquired after device_hotplug_lock.

This will make it possible to use device_hotplug_lock around some
code paths that acquire acpi_scan_lock safely (most importantly
system suspend and hibernation).  Apart from that, acpi_scan_lock
is platform-specific and device_hotplug_lock is general, so the
new ordering appears to be more appropriate from the overall
design viewpoint.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
PM / hibernate: Create memory bitmaps after freezing user space

The hibernation core uses special memory bitmaps during image
creation and restoration and traditionally those bitmaps are
allocated before freezing tasks, because in the past GFP_KERNEL
allocations might not work after all tasks had been frozen.

However, this is an anachronism, because hibernation_snapshot()
now calls hibernate_preallocate_memory() which allocates memory
for the image upfront anyway, so the memory bitmaps may be
allocated after freezing user space safely.

For this reason, move all of the create_basic_memory_bitmaps()
calls after freeze_processes() and all of the corresponding
free_basic_memory_bitmaps() calls before thaw_processes().

This will allow us to hold device_hotplug_lock around hibernation
without the need to worry about freezing issues with user space
processes attempting to acquire it via sysfs attributes after the
creation of memory bitmaps and before the freezing of tasks.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
PM / hibernate / memory hotplug: Rework mutual exclusion

Since all of the memory hotplug operations have to be carried out
under device_hotplug_lock, they won't need to acquire pm_mutex if
device_hotplug_lock is held around hibernation.

For this reason, make the hibernation code acquire
device_hotplug_lock after freezing user space processes and
release it before thawing them.  At the same tim drop the
lock_system_sleep() and unlock_system_sleep() calls from
lock_memory_hotplug() and unlock_memory_hotplug(), respectively.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
ACPI / LPSS: don't crash if a device has no MMIO resources

Intel LPSS devices that are enumerated from ACPI have both MMIO and IRQ
resources returned in their _CRS method. However, Apple Macbook Air with
Haswell has LPSS devices enumerated from PCI bus instead and _CRS method
returns only an interrupt number (but the device has _HID set that causes
the scan handler to match it).

The current ACPI / LPSS code sets pdata->dev_desc only when MMIO resource
is found for the device and in case of Macbook Air it is never found. That
leads to a NULL pointer dereference in register_device_clock().

Correct this by always setting the pdata->dev_desc.

Reported-and-tested-by: Imre Kaloz <kaloz@openwrt.org>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: 3.10+ <stable@vger.kernel.org> # 3.10+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
ACPI / hotplug / PCI: Don't trim devices before scanning the namespace

In acpiphp_bus_add() we first remove device objects corresponding to
the given handle and the ACPI namespace branch below it, which are
then re-created by acpi_bus_scan().  This used to be done to clean
up after surprise removals, but now we do the cleanup through
trim_stale_devices() which checks if the devices in question are
actually gone before removing them, so the device hierarchy trimming
in acpiphp_bus_add() is not necessary any more and, moreover, it may
lead to problems if it removes device objects corresponding to
devices that are actually present.

For this reason, remove the leftover acpiphp_bus_trim() from
acpiphp_bus_add().

Reported-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
ACPICA: Fix for a Store->ArgX when ArgX contains a reference to a field.

This change fixes a problem where a Store operation to an ArgX object
that contained a reference to a field object did not complete the
automatic dereference and then write to the actual field object.
Instead, the object type of the field object was inadvertently changed
to match the type of the source operand. The new behavior will actually
write to the field object (buffer field or field unit), thus matching
the correct ACPI-defined behavior.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
ACPI / hotplug / PCI: Avoid doing too much for spurious notifies

Sometimes we may get a spurious device check or bus check notify for
a hotplug device and in those cases we should avoid doing all of the
configuration work needed when something actually changes.  To that
end, check the return value of pci_scan_slot() in enable_slot() and
bail out early if it is 0.

This turns out to help reduce the amount of diagnostic output from
the ACPIPHP subsystem and speed up boot on at least one system that
generates multiple device check notifies for PCIe devices on the root
bus during boot.

Reported-and-tested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
ACPI / hotplug / PCI: Use _OST to notify firmware about notify status

The spec suggests that we should use _OST to notify the platform
about the status of notifications it sends us, for example so that
it doesn't repeate a notification that has been handled already.

This turns out to help reduce the amount of diagnostic output from
the ACPIPHP subsystem and speed up boot on at least one system that
generates multiple device check notifies for PCIe devices on the root
bus during boot.

Reported-and-tested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
ACPI / hotplug / PCI: Avoid parent bus rescans on spurious device checks

In the current ACPIPHP notify handler we always go directly for a
rescan of the parent bus if we get a device check notification for
a device that is not a bridge.  However, this obviously is
overzealous if nothing really changes, because this way we may rescan
the whole PCI hierarchy pretty much in vain.

That happens on Alex Williamson's machine whose ACPI tables contain
device objects that are supposed to coresspond to PCIe root ports,
but those ports aren't physically present (or at least they aren't
visible in the PCI config space to us).  The BIOS generates multiple
device check notifies for those objects during boot and for each of
them we go straight for the parent bus rescan, but the parent bus is
the root bus in this particular case.  In consequence, we rescan the
whole PCI bus from the top several times in a row, which is
completely unnecessary, increases boot time by 50% (after previous
fixes) and generates excess dmesg output from the PCI subsystem.

Fix the problem by checking if we can find anything new in the
slot corresponding to the device we've got a device check notify
for and doing nothig if that's not the case.

The spec (ACPI 5.0, Section 5.6.6) appears to mandate this behavior,
as it says:

  Device Check. Used to notify OSPM that the device either appeared
  or disappeared. If the device has appeared, OSPM will re-enumerate
  from the parent. If the device has disappeared, OSPM will
  invalidate the state of the device. OSPM may optimize out
  re-enumeration.

Therefore, according to the spec, we are free to do nothing if
nothing changes.

References: https://bugzilla.kernel.org/show_bug.cgi?id=60865
Reported-and-tested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Merge branch 'acpi-hotplug'

* acpi-hotplug:
  PM / hibernate / memory hotplug: Rework mutual exclusion
  PM / hibernate: Create memory bitmaps after freezing user space
  ACPI / scan: Change ordering of locks for device hotplug
Merge branch 'acpi-pci-hotplug'

* acpi-pci-hotplug:
  ACPI / hotplug / PCI: Avoid parent bus rescans on spurious device checks
  ACPI / hotplug / PCI: Use _OST to notify firmware about notify status
  ACPI / hotplug / PCI: Avoid doing too much for spurious notifies
  ACPI / hotplug / PCI: Don't trim devices before scanning the namespace
Merge branch 'acpica'

* acpica:
  ACPICA: Fix for a Store->ArgX when ArgX contains a reference to a field.
Merge branch 'acpi-assorted'

* acpi-assorted:
  ACPI / LPSS: don't crash if a device has no MMIO resources
Merge branch 'pm-cpuidle'

* pm-cpuidle:
  cpuidle: Check the result of cpuidle_get_driver() against NULL