ACPI: introduce CONFIG_ACPI_REDUCED_HARDWARE_ONLY

ACPI hardware reduced mode exists to allow newer platforms to use a
simpler form of ACPI that does not require supporting legacy versions
of the specification and their associated hardware.  This mode was
introduced in the ACPI 5.0 specification.

The ACPI hardware reduced mode is supposed to be used on systems
having the HW_REDUCED_ACPI flag set in the FADT.  ACPICA checks
that flag to determine whether or not it should work in the HW
reduced mode and there are pieces of code in it that will never
be used in that case.

Since some architecutres will always use the ACPI HW reduced mode,
it doesn't make sense for them to ever compile support for anything
else.  Thus, they should set the flag ACPI_REDUCED_HARDWARE to TRUE
in the ACPICA source.  To enable them to do that, introduce a new
kernel configuration option, CONFIG_ACPI_REDUCED_HARDWARE_ONLY, that
will cause the ACPICA's ACPI_REDUCED_HARDWARE flag to be TRUE when
set.

Introducing this configuration item is based on suggestions from Lv
Zheng saying that this does not belong in ACPICA, but rather to the
Linux kernel itself.

References: http://www.spinics.net/lists/linux-acpi/msg46369.html
Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Al Stone <al.stone@linaro.org>
[rjw: Subject and changelog]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
ACPI / hotplug / PCI: Simplify disable_slot()

After recent PCI core changes related to the rescan/remove locking,
the ACPIPHP's disable_slot() function is only called under the
general PCI rescan/remove lock, so it doesn't have to use
dev_in_slot() any more to avoid race conditions.  Make it simply
walk the devices on the bus and drop the ones in the slot being
disabled and drop dev_in_slot() which has no more users.

Moreover, to avoid problems described in the changelog of commit
29ed1f29b68a (PCI: pciehp: Fix null pointer deref when hot-removing
SR-IOV device), make disable_slot() carry out the list walk in
reverse order.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPI / hotplug / PCI: Proper kerneldoc comments for enumeration/removal

Add proper kerneldoc comments describing acpiphp_enumerate_slots()
and acpiphp_remove_slots().

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPI / hotplug / PCI: Simplify register_slot()

The err label in register_slot() is only jumped to from one place,
so move the code under the label to that place and drop the label.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPI / hotplug / PCI: Drop acpiphp_bus_trim()

If trim_stale_devices() calls acpi_bus_trim() directly, we can
save a potentially costly acpi_bus_get_device() invocation.  After
making that change acpiphp_bus_trim() would only be called from one
place, so move the code from it to that place and drop it.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPI / hotplug / PCI: Rework acpiphp_no_hotplug()

If a struct acpi_device pointer is passed to acpiphp_no_hotplug()
instead of an ACPI handle, the function won't need to call
acpi_bus_get_device(), which may be costly, any more.  Then,
trim_stale_devices() can call acpiphp_no_hotplug() passing
the struct acpi_device object it already has directly to that
function.

Make those changes and update slot_no_hotplug() accordingly.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPI / hotplug / PCI: Store acpi_device pointer in acpiphp_context

After recent modifications of the ACPI core making it create a struct
acpi_device object for every namespace node representing a device
regardless of the current status of that device the ACPIPHP code
can store a struct acpi_device pointer instead of an ACPI handle
in struct acpiphp_context.  This immediately makes it possible to
avoid making potentially costly calls to acpi_bus_get_device() in
two places and allows some more simplifications to be made going
forward.

The reason why that is correct is because ACPIPHP only installs
hotify handlers for namespace nodes that exist when
acpiphp_enumerate_slots() is called for their parent bridge.
That only happens if the parent bridge has an ACPI companion
associated with it, which means that the ACPI namespace scope
in question has been scanned already at that point.  That, in
turn, means that struct acpi_device objects have been created
for all namespace nodes in that scope and pointers to those
objects can be stored directly instead of their ACPI handles.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPI / hotplug / PCI: Drop acpiphp_bus_add()

acpiphp_bus_add() is only called from one place, so move the code out
of it into that place and drop it.  Also make that code use
func_to_acpi_device() to get the struct acpi_device pointer it needs
instead of calling acpi_bus_get_device() which may be costly.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPI / hotplug / PCI: Drop crit_sect locking

After recent PCI core changes related to the rescan/remove locking,
the code sections under crit_sect mutexes from ACPIPHP slot objects
are always executed under the general PCI rescan/remove lock.
For this reason, the crit_sect mutexes are simply redundant, so drop
them.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPI / hotplug / PCI: Simplify hotplug_event()

A few lines of code can be cut from hotplug_event() by defining
and initializing the slot variable at the top of the function,
so do that.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPI / hotplug / PCI: Use acpi_handle_debug() in hotplug_event()

Make hotplug_event() use acpi_handle_debug() instead of an open-coded
debug message printing and clean up the messages printed by it.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPI / hotplug / PCI: Do not pass ACPI handle to hotplug_event()

Since hotplug_event() can get the ACPI handle needed for debug
printouts from its context argument, there's no need to pass the
handle to it.  Moreover, the second argument's type may be changed
to (struct acpiphp_context *), because that's what is always passed
to hotplug_event() as the second argument anyway.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPICA: Introduce acpi_get_data_full() and rework acpi_get_data()

Introduce a new function, acpi_get_data_full(), working in analogy
with acpi_get_data() except that it can execute a callback provided
as its 4th argument right after acpi_ns_get_attached_data() has
returned a success.

That will allow Linux to reference count the object pointed to by
*data before the namespace mutex is released so as to ensure that it
will not be freed going forward until the reference to it acquired
by acpi_get_data_full() is dropped.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPI / hotplug: Fix potential race in acpi_bus_notify()

There is a slight possibility for the ACPI device object pointed to
by adev in acpi_hotplug_notify_cb() to become invalid between the
acpi_bus_get_device() that it comes from and the subsequent dereference
of that pointer under get_device().  Namely, if acpi_scan_drop_device()
runs in parallel with acpi_hotplug_notify_cb(), acpi_device_del_work_fn()
queued up by it may delete the device object in question right after
a successful execution of acpi_bus_get_device() in acpi_bus_notify().

An analogous problem is present in acpi_bus_notify() where the device
pointer coming from acpi_bus_get_device() may become invalid before
it subsequent dereference in the "if" block.

To prevent that from happening, introduce a new function,
acpi_bus_get_acpi_device(), working analogously to acpi_bus_get_device()
except that it will grab a reference to the ACPI device object returned
by it and it will do that under the ACPICA's namespace mutex.  Then,
make both acpi_hotplug_notify_cb() and acpi_bus_notify() use
acpi_bus_get_acpi_device() instead of acpi_bus_get_device() so as to
ensure that the pointers used by them will not become stale at one
point.

In addition to that, introduce acpi_bus_put_acpi_device() as a wrapper
around put_device() to be used along with acpi_bus_get_acpi_device()
and make the (new) users of the latter use acpi_bus_put_acpi_device()
too.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPI / hotplug / PCI: Define hotplug context lock in the core

Subsequent changes will require the ACPI core to acquire the lock
protecting the ACPIPHP hotplug contexts, so move the definition of
the lock to the core and change its name to be more generic.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPI / hotplug / PCI: Consolidate ACPIPHP with ACPI core hotplug

The ACPI-based PCI hotplug (ACPIPHP) code currently attaches its
hotplug context objects directly to ACPI namespace nodes representing
hotplug devices.  However, after recent changes causing struct
acpi_device to be created for every namespace node representing a
device (regardless of its status), that is not necessary any more.
Moreover, it's vulnerable to the theoretical issue that the ACPI
handle passed in the context between handle_hotplug_event() and
hotplug_event_work() may become invalid in the meantime (as a
result of a concurrent table unload).

In principle, this issue might be addressed by adding a non-empty
release handler for ACPIPHP hotplug context objects analogous to
acpi_scan_drop_device(), but that would duplicate the code in that
function and in acpi_device_del_work_fn().  For this reason, it's
better to modify ACPIPHP to attach its device hotplug contexts to
struct device objects representing hotplug devices and make it
use acpi_hotplug_notify_cb() as its notify handler.  At the same
time, acpi_device_hotplug() can be modified to dispatch the new
.hp.event() callback pointing to acpiphp_hotplug_event() from ACPI
device objects associated with PCI devices or use the generic
ACPI device hotplug code for device objects with matching scan
handlers.

This allows the existing code duplication between ACPIPHP and the
ACPI core to be reduced too and makes further ACPI-based device
hotplug consolidation possible.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
ACPI / hotplug / PCI: Rework the handling of eject requests

To avoid the need to install a hotplug notify handler for each ACPI
namespace node representing a device and having a matching scan
handler, move the check whether or not the ejection of the given
device is enabled through its scan handler from acpi_hotplug_notify_cb()
to acpi_generic_hotplug_event().  Also, move the execution of
ACPI_OST_SC_EJECT_IN_PROGRESS _OST to acpi_generic_hotplug_event(),
because in acpi_hotplug_notify_cb() or in acpi_eject_store() we really
don't know whether or not the eject is going to be in progress (for
example, acpi_hotplug_execute() may still fail without queuing up the
work item).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
ACPI / hotplug / PCI: Simplify acpi_install_hotplug_notify_handler()

Since acpi_hotplug_notify_cb() does not use its data argument any
more, the second argument of acpi_install_hotplug_notify_handler()
can be dropped, so do that and update its callers accordingly.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
ACPI / hotplug / PCI: Hotplug notifications from acpi_bus_notify()

Since acpi_bus_notify() is executed on all notifications for all
devices anyway, make it execute acpi_device_hotplug() for all
hotplug events instead of installing notify handlers pointing to
the same function for all hotplug devices.

This change reduces both the size and complexity of ACPI-based device
hotplug code.  Moreover, since acpi_device_hotplug() only does
significant things for devices that have either an ACPI scan handler,
or a hotplug context with .eject() defined, and those devices
had notify handlers pointing to acpi_hotplug_notify_cb() installed
before anyway, this modification shouldn't change functionality.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
ACPI / hotplug / PCI: Rework acpiphp_check_host_bridge()

Since the only existing caller of acpiphp_check_host_bridge(),
which is acpi_pci_root_scan_dependent(), already has a struct
acpi_device pointer needed to obtain the ACPIPHP context, it
doesn't make sense to execute acpi_bus_get_device() on its
handle in acpiphp_handle_to_bridge() just in order to get that
pointer back.

For this reason, modify acpiphp_check_host_bridge() to take
a struct acpi_device pointer as its argument and rearrange the
code accordingly.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>