Some sync_state() implementations might need to call APIs that in turn
make calls to device link APIs. So, do the sync_state() callbacks
without holding the device link lock.

Signed-off-by: Saravana Kannan <saravanak@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20191114225646.251277-1-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

When add_links() still has suppliers that it needs to link to in the
future, this patch allows it to differentiate between suppliers that are
needed for probing vs suppliers that are needed for sync_state()
correctness.

Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20191028220027.251605-4-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Before this change, if a device is waiting on suppliers, it's assumed
that all those suppliers are needed for the device to probe
successfully. This change allows marking a devices as waiting only on
optional suppliers. This allows a device to wait on suppliers (and link
to them as soon as they are available) without preventing the device
from being probed.

Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20191028220027.251605-3-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Parent devices might need to create "proxy" device links from themselves
to supplier devices to make sure the supplier devices don't get a
sync_state() before the child consumer devices get a chance to add
device links to the supplier devices.

However, the parent device has no real dependency on the supplier device
and probing, suspend/resume or runtime PM don't need to be affected by
the supplier device.  To capture these cases, create a SYNC_STATE_ONLY
device link flag that only affects sync_state() behavior and doesn't
affect probing, suspend/resume or runtime PM.

Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20191028220027.251605-2-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

We want the sysfs fix in here as well to build on top of.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

It is incorrect to set the cpufreq syscore shutdown callback pointer
to cpufreq_suspend(), because that function cannot be run in the
syscore stage of system shutdown for two reasons: (a) it may attempt
to carry out actions depending on devices that have already been shut
down at that point and (b) the RCU synchronization carried out by it
may not be able to make progress then.

The latter issue has been present since commit 45975c7d21a1 ("rcu:
Define RCU-sched API in terms of RCU for Tree RCU PREEMPT builds"),
but the former one has been there since commit 90de2a4aa9f3 ("cpufreq:
suspend cpufreq governors on shutdown") regardless.

Fix that by dropping cpufreq_syscore_ops altogether and making
device_shutdown() call cpufreq_suspend() directly before shutting
down devices, which is along the lines of what system-wide power
management does.

Fixes: 45975c7d21a1 ("rcu: Define RCU-sched API in terms of RCU for Tree RCU PREEMPT builds")
Fixes: 90de2a4aa9f3 ("cpufreq: suspend cpufreq governors on shutdown")
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: 4.0+ <stable@vger.kernel.org> # 4.0+

This sync_state driver/bus callback is called once all the consumers
of a supplier have probed successfully.

This allows the supplier device's driver/bus to sync the supplier
device's state to the software state with the guarantee that all the
consumers are actively managing the resources provided by the supplier
device.

To maintain backwards compatibility and ease transition from existing
frameworks and resource cleanup schemes, late_initcall_sync is the
earliest when the sync_state callback might be called.

There is no upper bound on the time by which the sync_state callback
has to be called. This is because if a consumer device never probes,
the supplier has to maintain its resources in the state left by the
bootloader. For example, if the bootloader leaves the display
backlight at a fixed voltage and the backlight driver is never probed,
you don't want the backlight to ever be turned off after boot up.

Also, when multiple devices are added after kernel init, some
suppliers could be added before their consumer devices get added. In
these instances, the supplier devices could get their sync_state
callback called right after they probe because the consumers devices
haven't had a chance to create device links to the suppliers.

To handle this correctly, this change also provides APIs to
pause/resume sync state callbacks so that when multiple devices are
added, their sync_state callback evaluation can be postponed to happen
after all of them are added.

kbuild test robot reported missing documentation for device.state_synced
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20190904211126.47518-5-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The firmware corresponding to a device (dev.fwnode) might be able to
provide functional dependency information between a device and its
supplier and consumer devices.  Tracking this functional dependency
allows optimizing device probe order and informing a supplier when all
its consumers have probed (and thereby actively managing their
resources).

The existing device links feature allows tracking and using
supplier-consumer relationships. So, this patch adds the add_links()
fwnode callback to allow firmware to create device links for each
device as the device is added.

However, when consumer devices are added, they might not have a supplier
device to link to despite needing mandatory resources/functionality from
one or more suppliers. A waiting_for_suppliers list is created to track
such consumers and retry linking them when new devices get added.

Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20190904211126.47518-3-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

It's often useful to look up a device that corresponds to a fwnode. So
add an API to do that irrespective of the bus on which the device has
been added to.

Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20190904211126.47518-2-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Pull driver core updates from Greg Kroah-Hartman:
 "Here is the big driver core update for 5.4-rc1.

  There was a bit of a churn in here, with a number of core and OF
  platform patches being added to the tree, and then after much
  discussion and review and a day-long in-person meeting, they were
  decided to be reverted and a new set of patches is currently being
  reviewed on the mailing list.

  Other than that churn, there are two "persistent" branches in here
  that other trees will be pulling in as well during the merge window.
  One branch to add support for drivers to have the driver core
  automatically add sysfs attribute files when a driver is bound to a
  device so that the driver doesn't have to manually do it (and then
  clean it up, as it always gets it wrong).

  There's another branch in here for generic lookup helpers for the
  driver core that lots of busses are starting to use. That's the
  majority of the non-driver-core changes in this patch series.

  There's also some on-going debugfs file creation cleanup that has been
  slowly happening over the past few releases, with the goal to
  hopefully get that done sometime next year.

  All of these have been in linux-next for a while now with no reported
  issues"

[ Note that the above-mentioned generic lookup helpers branch was
  already brought in by the LED merge (commit 4feaab05dc1e) that had
  shared it.

  Also note that that common branch introduced an i2c bug due to a bad
  conversion, which got fixed here. - Linus ]

* tag 'driver-core-5.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (49 commits)
  coccinelle: platform_get_irq: Fix parse error
  driver-core: add include guard to linux/container.h
  sysfs: add BIN_ATTR_WO() macro
  driver core: platform: Export platform_get_irq_optional()
  hwmon: pwm-fan: Use platform_get_irq_optional()
  driver core: platform: Introduce platform_get_irq_optional()
  Revert "driver core: Add support for linking devices during device addition"
  Revert "driver core: Add edit_links() callback for drivers"
  Revert "of/platform: Add functional dependency link from DT bindings"
  Revert "driver core: Add sync_state driver/bus callback"
  Revert "of/platform: Pause/resume sync state during init and of_platform_populate()"
  Revert "of/platform: Create device links for all child-supplier depencencies"
  Revert "of/platform: Don't create device links for default busses"
  Revert "of/platform: Fix fn definitons for of_link_is_valid() and of_link_property()"
  Revert "of/platform: Fix device_links_supplier_sync_state_resume() warning"
  Revert "of/platform: Disable generic device linking code for PowerPC"
  devcoredump: fix typo in comment
  devcoredump: use memory_read_from_buffer
  of/platform: Disable generic device linking code for PowerPC
  device.h: Fix warnings for mismatched parameter names in comments
  ...