Call the asynchronous probe routines on a CPU local to the device node. By
doing this we should be able to improve our initialization time
significantly as we can avoid having to access the device from a remote
node which may introduce higher latency.

For example, in the case of initializing memory for NVDIMM this can have a
significant impact as initialing 3TB on remote node can take up to 39
seconds while initialing it on a local node only takes 23 seconds. It is
situations like this where we will see the biggest improvement.
Reviewed-by: NDan Williams <dan.j.williams@intel.com>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NAlexander Duyck <alexander.h.duyck@linux.intel.com>
Reviewed-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Probe devices asynchronously instead of the driver. This results in us
seeing the same behavior if the device is registered before the driver or
after. This way we can avoid serializing the initialization should the
driver not be loaded until after the devices have already been added.

The motivation behind this is that if we have a set of devices that
take a significant amount of time to load we can greatly reduce the time to
load by processing them in parallel instead of one at a time. In addition,
each device can exist on a different node so placing a single thread on one
CPU to initialize all of the devices for a given driver can result in poor
performance on a system with multiple nodes.

This approach can reduce the time needed to scan SCSI LUNs significantly.
The only way to realize that speedup is by enabling more concurrency which
is what is achieved with this patch.

To achieve this it was necessary to add a new member "async_driver" to the
device_private structure to store the driver pointer while we wait on the
deferred probe call.
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Reviewed-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NAlexander Duyck <alexander.h.duyck@linux.intel.com>
Reviewed-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Try to consolidate all of the locking and unlocking of both the parent and
device when attaching or removing a driver from a given device.

To do that I first consolidated the lock pattern into two functions
__device_driver_lock and __device_driver_unlock. After doing that I then
created functions specific to attaching and detaching the driver while
acquiring these locks. By doing this I was able to reduce the number of
spots where we touch need_parent_lock from 12 down to 4.

This patch should produce no functional changes, it is meant to be a code
clean-up/consolidation only.
Reviewed-by: NLuis Chamberlain <mcgrof@kernel.org>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Reviewed-by: NDan Williams <dan.j.williams@intel.com>
Reviewed-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NAlexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Add an additional bit flag to the device_private struct named "dead".

This additional flag provides a guarantee that when a device_del is
executed on a given interface an async worker will not attempt to attach
the driver following the earlier device_del call. Previously this
guarantee was not present and could result in the device_del call
attempting to remove a driver from an interface only to have the async
worker attempt to probe the driver later when it finally completes the
asynchronous probe call.

One additional change added was that I pulled the check for dev->driver
out of the __device_attach_driver call and instead placed it in the
__device_attach_async_helper call. This was motivated by the fact that the
only other caller of this, __device_attach, had already taken the
device_lock() and checked for dev->driver. Instead of testing for this
twice in this path it makes more sense to just consolidate the dev->dead
and dev->driver checks together into one set of checks.
Reviewed-by: NDan Williams <dan.j.williams@intel.com>
Reviewed-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NAlexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

__device_release_driver() has to check dev->bus->need_parent_lock
before dropping the parent lock and acquiring it again as it may
attempt to drop a lock that hasn't been acquired or lock a device
that shouldn't be locked and create a lock imbalance.

Fixes: 8c97a46a (driver core: hold dev's parent lock when needed)
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: stable <stable@vger.kernel.org>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Move the async_synchronize_full call out of __device_release_driver and
into driver_detach.

The idea behind this is that the async_synchronize_full call will only
guarantee that any existing async operations are flushed. This doesn't do
anything to guarantee that a hotplug event that may occur while we are
doing the release of the driver will not be asynchronously scheduled.

By moving this into the driver_detach path we can avoid potential deadlocks
as we aren't holding the device lock at this point and we should not have
the driver we want to flush loaded so the flush will take care of any
asynchronous events the driver we are detaching might have scheduled.

Fixes: 765230b5 ("driver-core: add asynchronous probing support for drivers")
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Reviewed-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NAlexander Duyck <alexander.h.duyck@linux.intel.com>
Reviewed-by: NLuis Chamberlain <mcgrof@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Correct function name and spelling/typo for device_block_probing()
in drivers/base/dd.c.
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Reviewed-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The simple_strtol() function is deprecated, use kstrtoint() instead.
Signed-off-by: NMuchun Song <smuchun@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This goes through a lot of hooks just to call arch_teardown_dma_ops.
Replace it with a direct call instead.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NRobin Murphy <robin.murphy@arm.com>

There is no good reason for this indirection given that the method
always exists.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NRobin Murphy <robin.murphy@arm.com>

Commit 52cdbdd4 (driver core: correct device's shutdown order)
introduced a regression by breaking device shutdown on some systems.

Namely, the devices_kset_move_last() call in really_probe() added by
that commit is a mistake as it may cause parents to follow children
in the devices_kset list which then causes shutdown to fail.  For
example, if a device has children before really_probe() is called
for it (which is not uncommon), that call will cause it to be
reordered after the children in the devices_kset list and the
ordering of that list will not reflect the correct device shutdown
order any more.

Also it causes the devices_kset list to be constantly reordered
until all drivers have been probed which is totally pointless
overhead in the majority of cases and it only covered an issue
with system shutdown, while system-wide suspend/resume potentially
had the same issue on the affected platforms (which was not covered).

Moreover, the shutdown issue originally addressed by the change in
really_probe() made by commit 52cdbdd4 is not present in 4.18-rc
any more, since dra7 started to use the sdhci-omap driver which
doesn't disable any regulators during shutdown, so the really_probe()
part of commit 52cdbdd4 can be safely reverted.  [The original
issue was related to the omap_hsmmc driver used by dra7 previously.]

For the above reasons, revert the really_probe() modifications made
by commit 52cdbdd4.

The other code changes made by commit 52cdbdd4 are useful and
they need not be reverted.

Fixes: 52cdbdd4 (driver core: correct device's shutdown order)
Link: https://lore.kernel.org/lkml/CAFgQCTt7VfqM=UyCnvNFxrSw8Z6cUtAi3HUwR4_xPAc03SgHjQ@mail.gmail.com/Reported-by: NPingfan Liu <kernelfans@gmail.com>
Tested-by: NPingfan Liu <kernelfans@gmail.com>
Reviewed-by: NKishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Deferred probe will currently wait forever on dependent devices to probe,
but sometimes a driver will never exist. It's also not always critical for
a driver to exist. Platforms can rely on default configuration from the
bootloader or reset defaults for things such as pinctrl and power domains.
This is often the case with initial platform support until various drivers
get enabled. There's at least 2 scenarios where deferred probe can render
a platform broken. Both involve using a DT which has more devices and
dependencies than the kernel supports. The 1st case is a driver may be
disabled in the kernel config. The 2nd case is the kernel version may
simply not have the dependent driver. This can happen if using a newer DT
(provided by firmware perhaps) with a stable kernel version. Deferred
probe issues can be difficult to debug especially if the console has
dependencies or userspace fails to boot to a shell.

There are also cases like IOMMUs where only built-in drivers are
supported, so deferring probe after initcalls is not needed. The IOMMU
subsystem implemented its own mechanism to handle this using OF_DECLARE
linker sections.

This commit adds makes ending deferred probe conditional on initcalls
being completed or a debug timeout. Subsystems or drivers may opt-in by
calling driver_deferred_probe_check_init_done() instead of
unconditionally returning -EPROBE_DEFER. They may use additional
information from DT or kernel's config to decide whether to continue to
defer probe or not.

The timeout mechanism is intended for debug purposes and WARNs loudly.
The remaining deferred probe pending list will also be dumped after the
timeout. Not that this timeout won't work for the console which needs
to be enabled before userspace starts. However, if the console's
dependencies are resolved, then the kernel log will be printed (as
opposed to no output).

Cc: Alexander Graf <agraf@suse.de>
Signed-off-by: NRob Herring <robh@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

With Device Trees (DT), the dependencies of the devices are defined in the
DT, then the drivers parse that information to lookup the needed resources
that have as dependencies.

Since drivers and devices are registered in a non-deterministic way, it is
possible that a device that is a dependency has not been registered yet by
the time that is looked up.

In this case the driver that requires this dependency cannot probe and has
to defer it. So the driver core adds it to a list of deferred devices that
is iterated again every time that a new driver is probed successfully.

For debugging purposes it may be useful to know what are the devices whose
probe function was deferred. Add a debugfs entry showing that information.

  $ cat /sys/kernel/debug/devices_deferred
  48070000.i2c:twl@48:bci
  musb-hdrc.0.auto
  omapdrm.0

This information could be obtained partially by enabling debugging, but it
means that the kernel log has to be parsed and the probe deferral balanced
with the successes. This can be error probe and has to be done in a ad-hoc
manner by everyone who needs to debug these kind of issues.

Since the information is already known by the kernel, just show it to make
it easier to debug.
Signed-off-by: NJavier Martinez Canillas <javierm@redhat.com>
Reviewed-by: NAndy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: NMark Brown <broonie@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Add initcall_debug logs for each driver device probe call, for example:

   probe of a3800000.ramoops returned 1 after 3007 usecs

This replaces the previous code added to report times for deferred
probes.  It also reports OF platform bus device creates that were
formerly lumped together in a single entry for function
of_platform_default_populate_init, as well as helping to annotate other
initcalls that involve device probing.

Remove restriction on printing probe times only during initcalls, since
initcall_debug now continues to show driver timing info past the boot
phase.
Signed-off-by: NTodd Poynor <toddpoynor@google.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Revert commit 1e837861 (PM / runtime: Fixup reference counting of
device link suppliers at probe), as it has introduced a regression
and the condition it was designed to address should be covered by the
existing code.
Reported-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

SoC have internal I/O buses that can't be proved for devices. The
devices on the buses can be accessed directly without additinal
configuration required. This type of bus is represented as
"simple-bus". In some platforms, we name "soc" with "simple-bus"
attribute and many devices are hooked under it described in DT
(device tree).

In commit bf74ad5b ("Hold the device's parent's lock during
probe and remove") to solve USB subsystem lock sequence since
USB device's characteristic. Thus "soc" needs to be locked
whenever a device and driver's probing happen under "soc" bus.
During this period, an async driver tries to probe a device which
is under the "soc" bus would be blocked until previous driver
finish the probing and release "soc" lock. And the next probing
under the "soc" bus need to wait for async finish. Because of
that, driver's async probe for init time improvement will be
shadowed.

Since many devices don't have USB devices' characteristic, they
actually don't need parent's lock. Thus, we introduce a lock flag
in bus_type struct and driver core would lock the parent lock base
on the flag. For USB, we set this flag in usb_bus_type to keep
original lock behavior in driver core.

Async probe could have more benefit after this patch.
Signed-off-by: NMartin Liu <liumartin@google.com>
Acked-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

In the driver core, before it invokes really_probe() it runtime resumes the
suppliers for the device via calling pm_runtime_get_suppliers(), which also
increases the runtime PM usage count for each of the available supplier.

This makes sense, as to be able to allow the consumer device to be probed
by its driver. However, if the driver decides to add a new supplier link
during ->probe(), hence updating the list of suppliers, the following call
to pm_runtime_put_suppliers(), invoked after really_probe() in the driver
core, we get into trouble.

More precisely, pm_runtime_put() gets called also for the new supplier(s),
which is wrong as the driver core, didn't trigger pm_runtime_get_sync() to
be called for it in the first place. In other words, the new supplier may
be runtime suspended even in cases when it shouldn't.

Fix this behaviour, by runtime resume suppliers according to the same
conditions as managed by the runtime PM core, when runtime resume callbacks
are being invoked.

Additionally, don't try to runtime suspend any of the suppliers after
really_probe(), but instead rely on that to happen via the consumer device,
when it becomes runtime suspended.

Fixes: 21d5c57b (PM / runtime: Use device links)
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

When bridge and its endpoint is enumerated the devices are added to the
dpm list. Afterward, the bridge defers probe when IOMMU is not ready.
This causes the bridge to be moved to the end of the dpm list when
deferred probe kicks in. The order of the dpm list for bridge and
endpoint is reversed.

Add reordering code to move the bridge and its children and consumers to
the end of the pm list so the order for suspend and resume is not altered.
The code also move device and its children and consumers to the tail of
device_kset list if it is registered.
Signed-off-by: NToan Le <toanle@apm.com>
Signed-off-by: NFeng Kan <fkan@apm.com>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

The check for the .coredump() callback in coredump_store() is
redundant. It is already assured the device driver implements
the callback upon creating the coredump sysfs entry.
Signed-off-by: NArend van Spriel <aspriel@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This adds the coredump driver operation. When the driver defines it
a coredump file is added in the sysfs folder of the device upon
driver binding. The file is removed when the driver is unbound.
User-space can trigger a coredump for this device by echo'ing to
the coredump file.
Signed-off-by: NArend van Spriel <aspriel@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Now that the SPDX tag is in all driver core files, that identifies the
license in a specific and legally-defined manner.  So the extra GPL text
wording can be removed as it is no longer needed at all.

This is done on a quest to remove the 700+ different ways that files in
the kernel describe the GPL license text.  And there's unneeded stuff
like the address (sometimes incorrect) for the FSF which is never
needed.

No copyright headers or other non-license-description text was removed.

Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

It's good to have SPDX identifiers in all files to make it easier to
audit the kernel tree for correct licenses.

Update the driver core files files with the correct SPDX license
identifier based on the license text in the file itself.  The SPDX
identifier is a legally binding shorthand, which can be used instead of
the full boiler plate text.

This work is based on a script and data from Thomas Gleixner, Philippe
Ombredanne, and Kate Stewart.

Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: William Breathitt Gray <vilhelm.gray@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

A device probe deferred because of a device link is never probed again
because it is not added to the deferred_probe_pending_list. Add it, taking
care of the race with driver_deferred_probe_trigger().
Signed-off-by: NAdrian Hunter <adrian.hunter@intel.com>
Reviewed-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The motivation for this change is to provide a way to work around
a problem with the direct-complete mechanism used for avoiding
system suspend/resume handling for devices in runtime suspend.

The problem is that some middle layer code (the PCI bus type and
the ACPI PM domain in particular) returns positive values from its
system suspend ->prepare callbacks regardless of whether the driver's
->prepare returns a positive value or 0, which effectively prevents
drivers from being able to control the direct-complete feature.
Some drivers need that control, however, and the PCI bus type has
grown its own flag to deal with this issue, but since it is not
limited to PCI, it is better to address it by adding driver flags at
the core level.

To that end, add a driver_flags field to struct dev_pm_info for flags
that can be set by device drivers at the probe time to inform the PM
core and/or bus types, PM domains and so on on the capabilities and/or
preferences of device drivers.  Also add two static inline helpers
for setting that field and testing it against a given set of flags
and make the driver core clear it automatically on driver remove
and probe failures.

Define and document two PM driver flags related to the direct-
complete feature: NEVER_SKIP and SMART_PREPARE that can be used,
respectively, to indicate to the PM core that the direct-complete
mechanism should never be used for the device and to inform the
middle layer code (bus types, PM domains etc) that it can only
request the PM core to use the direct-complete mechanism for
the device (by returning a positive value from its ->prepare
callback) if it also has been requested by the driver.

While at it, make the core check pm_runtime_suspended() when
setting power.direct_complete so that it doesn't need to be
checked by ->prepare callbacks.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NUlf Hansson <ulf.hansson@linaro.org>

initcall_debug attributes all deferred device probe retries for the
late_initcall level to function deferred_probe_initcall.  Add logs of
the individual device probe routines called, to identify which drivers
are executing for how long during the initcall path.  Deferred probes
that occur after initcall processing are not shown.

Example log messages added:

[    0.505119] deferred probe my-sound-device @ 6
[    0.517656] deferred probe my-sound-device returned after 1227 usecs
Signed-off-by: NTodd Poynor <toddpoynor@google.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

There are certain touch controllers that may come up in either normal
(application) or boot mode, depending on whether firmware/configuration is
corrupted when they are powered on. In boot mode the kernel does not create
input device instance (because it does not necessarily know the
characteristics of the input device in question).

Another number of controllers does not store firmware in a non-volatile
memory, and they similarly need to have firmware loaded before input device
instance is created. There are also other types of devices with similar
behavior.

There is a desire to be able to trigger firmware loading via udev, but it
has to happen only when driver is bound to a physical device (i2c or spi).
These udev actions can not use ADD events, as those happen too early, so we
are introducing BIND and UNBIND events that are emitted at the right
moment.

Also, many drivers create additional driver-specific device attributes
when binding to the device, to provide userspace with additional controls.
The new events allow userspace to adjust these driver-specific attributes
without worrying that they are not there yet.
Signed-off-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Configuring DMA ops at probe time will allow deferring device probe when
the IOMMU isn't available yet. The dma_configure for the device is
now called from the generic device_attach callback just before the
bus/driver probe is called. This way, configuring the DMA ops for the
device would be called at the same place for all bus_types, hence the
deferred probing mechanism should work for all buses as well.

pci_bus_add_devices    (platform/amba)(_device_create/driver_register)
       |                         |
pci_bus_add_device     (device_add/driver_register)
       |                         |
device_attach           device_initial_probe
       |                         |
__device_attach_driver    __device_attach_driver
       |
driver_probe_device
       |
really_probe
       |
dma_configure

Similarly on the device/driver_unregister path __device_release_driver is
called which inturn calls dma_deconfigure.

This patch changes the dma ops configuration to probe time for
both OF and ACPI based platform/amba/pci bus devices.
Tested-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Tested-by: NHanjun Guo <hanjun.guo@linaro.org>
Reviewed-by: NRobin Murphy <robin.murphy@arm.com>
Acked-by: NRob Herring <robh@kernel.org>
Acked-by: Bjorn Helgaas <bhelgaas@google.com> (drivers/pci part)
Acked-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NSricharan R <sricharan@codeaurora.org>
Signed-off-by: NJoerg Roedel <jroedel@suse.de>

This reverts commit 6751667a.

Rob Herring objected to it, and a replacement for it will be added using
debugfs in the future.

Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>
Reported-by: NRob Herring <robh@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

It is sometimes useful to know that a device is on the deferred probe
list rather than, say, not having a driver available.  Expose this
information to user-space.
Signed-off-by: NBen Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Modify the runtime PM framework to use device links to ensure that
supplier devices will not be suspended if any of their consumer
devices are active.

The idea is to reference count suppliers on the consumer's resume
and drop references to them on its suspend.  The information on
whether or not the supplier has been reference counted by the
consumer's (runtime) resume is stored in a new field (rpm_active)
in the link object for each link.

It may be necessary to clean up those references when the
supplier is unbinding and that's why the links whose status is
DEVICE_LINK_SUPPLIER_UNBIND are skipped by the runtime suspend
and resume code.

The above means that if the consumer device is probed in the
runtime-active state, the supplier has to be resumed and reference
counted by device_link_add() so the code works as expected on its
(runtime) suspend.  There is a new flag, DEVICE_LINK_RPM_ACTIVE,
to tell device_link_add() about that (in which case the caller
is responsible for making sure that the consumer really will
be runtime-active when runtime PM is enabled for it).

The other new link flag, DEVICE_LINK_PM_RUNTIME, tells the core
whether or not the link should be used for runtime PM at all.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Currently, there is a problem with taking functional dependencies
between devices into account.

What I mean by a "functional dependency" is when the driver of device
B needs device A to be functional and (generally) its driver to be
present in order to work properly.  This has certain consequences
for power management (suspend/resume and runtime PM ordering) and
shutdown ordering of these devices.  In general, it also implies that
the driver of A needs to be working for B to be probed successfully
and it cannot be unbound from the device before the B's driver.

Support for representing those functional dependencies between
devices is added here to allow the driver core to track them and act
on them in certain cases where applicable.

The argument for doing that in the driver core is that there are
quite a few distinct use cases involving device dependencies, they
are relatively hard to get right in a driver (if one wants to
address all of them properly) and it only gets worse if multiplied
by the number of drivers potentially needing to do it.  Morever, at
least one case (asynchronous system suspend/resume) cannot be handled
in a single driver at all, because it requires the driver of A to
wait for B to suspend (during system suspend) and the driver of B to
wait for A to resume (during system resume).

For this reason, represent dependencies between devices as "links",
with the help of struct device_link objects each containing pointers
to the "linked" devices, a list node for each of them, status
information, flags, and an RCU head for synchronization.

Also add two new list heads, representing the lists of links to the
devices that depend on the given one (consumers) and to the devices
depended on by it (suppliers), and a "driver presence status" field
(needed for figuring out initial states of device links) to struct
device.

The entire data structure consisting of all of the lists of link
objects for all devices is protected by a mutex (for link object
addition/removal and for list walks during device driver probing
and removal) and by SRCU (for list walking in other case that will
be introduced by subsequent change sets).  If CONFIG_SRCU is not
selected, however, an rwsem is used for protecting the entire data
structure.

In addition, each link object has an internal status field whose
value reflects whether or not drivers are bound to the devices
pointed to by the link or probing/removal of their drivers is in
progress etc.  That field is only modified under the device links
mutex, but it may be read outside of it in some cases (introduced by
subsequent change sets), so modifications of it are annotated with
WRITE_ONCE().

New links are added by calling device_link_add() which takes three
arguments: pointers to the devices in question and flags.  In
particular, if DL_FLAG_STATELESS is set in the flags, the link status
is not to be taken into account for this link and the driver core
will not manage it.  In turn, if DL_FLAG_AUTOREMOVE is set in the
flags, the driver core will remove the link automatically when the
consumer device driver unbinds from it.

One of the actions carried out by device_link_add() is to reorder
the lists used for device shutdown and system suspend/resume to
put the consumer device along with all of its children and all of
its consumers (and so on, recursively) to the ends of those lists
in order to ensure the right ordering between all of the supplier
and consumer devices.

For this reason, it is not possible to create a link between two
devices if the would-be supplier device already depends on the
would-be consumer device as either a direct descendant of it or a
consumer of one of its direct descendants or one of its consumers
and so on.

There are two types of link objects, persistent and non-persistent.
The persistent ones stay around until one of the target devices is
deleted, while the non-persistent ones are removed automatically when
the consumer driver unbinds from its device (ie. they are assumed to
be valid only as long as the consumer device has a driver bound to
it).  Persistent links are created by default and non-persistent
links are created when the DL_FLAG_AUTOREMOVE flag is passed
to device_link_add().

Both persistent and non-persistent device links can be deleted
with an explicit call to device_link_del().

Links created without the DL_FLAG_STATELESS flag set are managed
by the driver core using a simple state machine.  There are 5 states
each link can be in: DORMANT (unused), AVAILABLE (the supplier driver
is present and functional), CONSUMER_PROBE (the consumer driver is
probing), ACTIVE (both supplier and consumer drivers are present and
functional), and SUPPLIER_UNBIND (the supplier driver is unbinding).
The driver core updates the link state automatically depending on
what happens to the linked devices and for each link state specific
actions are taken in addition to that.

For example, if the supplier driver unbinds from its device, the
driver core will also unbind the drivers of all of its consumers
automatically under the assumption that they cannot function
properly without the supplier.  Analogously, the driver core will
only allow the consumer driver to bind to its device if the
supplier driver is present and functional (ie. the link is in
the AVAILABLE state).  If that's not the case, it will rely on
the existing deferred probing mechanism to wait for the supplier
driver to become available.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit d42a09802174 (driver core: skip removal test for non-removable
drivers) introduced a smatch warning:

drivers/base/dd.c:386 really_probe()
         warn: variable dereferenced before check 'dev->bus' (see line 373)

Fix the warning by removing the dev->bus NULL check. dev->bus will never
be NULL, so the check was unnecessary.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NRob Herring <robh@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Some drivers do not support removal/unbinding. These drivers should have
drv->suppress_bind_attrs set to true, so use that to skip the removal
test.

This doesn't fix anything reported so far, but should prevent some other
cases. Some drivers will need fixes to set suppress_bind_attrs to avoid
this test.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=177021
Fixes: bea5b158 ("driver core: add test of driver remove calls during probe")
Reported-by: NLaszlo Ersek <lersek@redhat.com>
Signed-off-by: NRob Herring <robh@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Add an internal wrapper around __device_release_driver() that will
acquire device locks and do the necessary checks before calling it.

The next patch will make use of it.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The workqueue "deferred_wq" queues a single work item
&deferred_probe_work and hence doesn't require ordering.
It is involved in probing devices and is not being used on a memory
reclaim path. Hence, it has been converted to use system_wq.

System workqueues have been able to handle high level of concurrency
for a long time now and hence it's not required to have a singlethreaded
workqueue just to gain concurrency. Unlike a dedicated per-cpu workqueue
created with create_singlethread_workqueue(), system_wq allows multiple
work items to overlap executions even on the same CPU; however, a
per-cpu workqueue doesn't have any CPU locality or global ordering
guarantee unless the target CPU is explicitly specified and thus the
increase of local concurrency shouldn't make any difference.

The work item has been flushed in driver_probe_done() to ensure that
there are no pending tasks while disconnecting the driver.
Signed-off-by: NBhaktipriya Shridhar <bhaktipriya96@gmail.com>
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

In recent discussions on ksummit-discuss[1], it was suggested to do a
sequence of probe, remove, probe for testing driver remove paths. This
adds a kconfig option for said test.

[1] https://lists.linuxfoundation.org/pipermail/ksummit-discuss/2016-August/003459.htmlSuggested-by: NArnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NRob Herring <robh@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This reverts commit ded9db38.

Thierry Reding writes:
	This causes a boot regression on at least one board, caused by
	one of the drivers looking at driver data to check whether or
	not the driver has properly loaded. If the code encounters a
	non-NULL pointer it tries to dereference it, but because it's
	already been freed there is no memory backing it and things
	crash.

	I don't think keeping stale pointers around is a good idea. The
	whole point of setting this to NULL in the core is so that probe
	failures result in the same starting conditions no matter what.

	Can we please get this reverted?
Reported-by: NThierry Reding <thierry.reding@gmail.com>
Cc: Yi Zhang <yizhang_hust@163.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

the driver_data may be used for sanity check, it fails the
probe() if driver_data is NULL after it is re-triggered.
for example, soc_probe() in sound/soc/soc-core.c
Signed-off-by: NYi Zhang <yizhang_hust@163.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Allow implementations of the match() callback in struct bus_type to
return errors and if it's -EPROBE_DEFER then queue the device for
deferred probing.

This is useful to buses such as AMBA in which devices are registered
before their matching information can be retrieved from the HW
(typically because a clock driver hasn't probed yet).

[changed if-else code structure, adjusted documentation to match the code,
extended comments]
Signed-off-by: NTomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: NUlf Hansson <ulf.hansson@linaro.org>
Acked-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

If device_is_bound() is called on a device that's not been registered
yet, it will attepmt to dereference dev->p which is NULL, so avoid
that by checking dev->p in there against NULL.

Fixes: 6b9cb427 "device core: add device_is_bound()"
Reported-and-tested-by: NGuenter Roeck <linux@roeck-us.net>
Tested-by: NTony Lindgren <tony@atomide.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>