linux-toradex.git/drivers/base/core.c, branch v6.9-rc4

driver core: Introduce device_link_wait_removal()

2024-03-26T20:32:32+00:00

The commit 80dd33cf72d1 ("drivers: base: Fix device link removal")
introduces a workqueue to release the consumer and supplier devices used
in the devlink.
In the job queued, devices are release and in turn, when all the
references to these devices are dropped, the release function of the
device itself is called.

Nothing is present to provide some synchronisation with this workqueue
in order to ensure that all ongoing releasing operations are done and
so, some other operations can be started safely.

For instance, in the following sequence:
  1) of_platform_depopulate()
  2) of_overlay_remove()

During the step 1, devices are released and related devlinks are removed
(jobs pushed in the workqueue).
During the step 2, OF nodes are destroyed but, without any
synchronisation with devlink removal jobs, of_overlay_remove() can raise
warnings related to missing of_node_put():
  ERROR: memory leak, expected refcount 1 instead of 2

Indeed, the missing of_node_put() call is going to be done, too late,
from the workqueue job execution.

Introduce device_link_wait_removal() to offer a way to synchronize
operations waiting for the end of devlink removals (i.e. end of
workqueue jobs).
Also, as a flushing operation is done on the workqueue, the workqueue
used is moved from a system-wide workqueue to a local one.

Cc: stable@vger.kernel.org
Signed-off-by: Herve Codina 
Tested-by: Luca Ceresoli 
Reviewed-by: Nuno Sa 
Reviewed-by: Saravana Kannan 
Acked-by: Greg Kroah-Hartman 
Link: https://lore.kernel.org/r/20240325152140.198219-2-herve.codina@bootlin.com
Signed-off-by: Rob Herring

driver core: Add FWLINK_FLAG_IGNORE to completely ignore a fwnode link

2024-03-07T22:10:01+00:00

A fwnode link between specific supplier-consumer fwnodes can be added
multiple times for multiple reasons. If that dependency doesn't exist,
deleting the fwnode link once doesn't guarantee that it won't get created
again.

So, add FWLINK_FLAG_IGNORE flag to mark a fwnode link as one that needs to
be completely ignored. Since a fwnode link's flags is an OR of all the
flags passed to all the fwnode_link_add() calls to create that specific
fwnode link, the FWLINK_FLAG_IGNORE flag is preserved and can be used to
mark a fwnode link as on that need to be completely ignored until it is
deleted.

Signed-off-by: Saravana Kannan 
Acked-by: "Rafael J. Wysocki" 
Reviewed-by: Rob Herring 
Link: https://lore.kernel.org/r/20240305050458.1400667-3-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman

driver core: Adds flags param to fwnode_link_add()

2024-03-07T22:10:01+00:00

Allow the callers to set fwnode link flags when adding fwnode links.

Signed-off-by: Saravana Kannan 
Acked-by: "Rafael J. Wysocki" 
Reviewed-by: Rob Herring 
Link: https://lore.kernel.org/r/20240305050458.1400667-2-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman

driver core: Move fw_devlink stuff to where it belongs

2024-03-07T22:07:22+00:00

A few APIs, i.e. fwnode_is_ancestor_of(), fwnode_get_next_parent_dev(),
and get_dev_from_fwnode(), that belong specifically to the fw_devlink APIs,
may be static, but they are not.

Resolve this mess by moving them to the driver/base/core where the all
users are being resided and make static.

No functional changes intended.

Reviewed-by: Sakari Ailus 
Acked-by: "Rafael J. Wysocki" 
Signed-off-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20240301180138.271590-3-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

driver core: fw_devlink: Improve logs for cycle detection

2024-02-02T15:12:33+00:00

The links in a cycle are not all logged in a consistent manner or not
logged at all. Make them consistent by adding a "cycle:" string and log all
the link in the cycles (even the child ==> parent dependency) so that it's
easier to debug cycle detection code. Also, mark the start and end of a
cycle so it's easy to tell when multiple cycles are logged back to back.

Signed-off-by: Saravana Kannan 
Tested-by: Xu Yang 
Link: https://lore.kernel.org/r/20240202095636.868578-4-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman

driver core: fw_devlink: Improve detection of overlapping cycles

2024-02-02T15:12:33+00:00

fw_devlink can detect most overlapping/intersecting cycles. However it was
missing a few corner cases because of an incorrect optimization logic that
tries to avoid repeating cycle detection for devices that are already
marked as part of a cycle.

Here's an example provided by Xu Yang (edited for clarity):

                    usb
                  +-----+
   tcpc           |     |
  +-----+         |  +--|
  |     |----------->|EP|
  |--+  |         |  +--|
  |EP|<-----------|     |
  |--+  |         |  B  |
  |     |         +-----+
  |  A  |            |
  +-----+            |
     ^     +-----+   |
     |     |     |   |
     +-----|  C  |<--+
           |     |
           +-----+
           usb-phy

Node A (tcpc) will be populated as device 1-0050.
Node B (usb) will be populated as device 38100000.usb.
Node C (usb-phy) will be populated as device 381f0040.usb-phy.

The description below uses the notation:
consumer --> supplier
child ==> parent

1. Node C is populated as device C. No cycles detected because cycle
   detection is only run when a fwnode link is converted to a device link.

2. Node B is populated as device B. As we convert B --> C into a device
   link we run cycle detection and find and mark the device link/fwnode
   link cycle:
   C--> A --> B.EP ==> B --> C

3. Node A is populated as device A. As we convert C --> A into a device
   link, we see it's already part of a cycle (from step 2) and don't run
   cycle detection. Thus we miss detecting the cycle:
   A --> B.EP ==> B --> A.EP ==> A

Looking at it another way, A depends on B in one way:
A --> B.EP ==> B

But B depends on A in two ways and we only detect the first:
B --> C --> A
B --> A.EP ==> A

To detect both of these, we remove the incorrect optimization attempt in
step 3 and run cycle detection even if the fwnode link from which the
device link is being created has already been marked as part of a cycle.

Reported-by: Xu Yang 
Closes: https://lore.kernel.org/lkml/DU2PR04MB8822693748725F85DC0CB86C8C792@DU2PR04MB8822.eurprd04.prod.outlook.com/
Fixes: 3fb16866b51d ("driver core: fw_devlink: Make cycle detection more robust")
Signed-off-by: Saravana Kannan 
Tested-by: Xu Yang 
Link: https://lore.kernel.org/r/20240202095636.868578-3-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman

driver core: Fix device_link_flag_is_sync_state_only()

2024-02-02T15:12:33+00:00

device_link_flag_is_sync_state_only() correctly returns true on the flags
of an existing device link that only implements sync_state() functionality.
However, it incorrectly and confusingly returns false if it's called with
DL_FLAG_SYNC_STATE_ONLY.

This bug doesn't manifest in any of the existing calls to this function,
but fix this confusing behavior to avoid future bugs.

Fixes: 67cad5c67019 ("driver core: fw_devlink: Add DL_FLAG_CYCLE support to device links")
Signed-off-by: Saravana Kannan 
Tested-by: Xu Yang 
Link: https://lore.kernel.org/r/20240202095636.868578-2-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman

driver core: Better advertise dev_err_probe()

2023-12-15T17:54:18+00:00

Describing the usage of dev_err_probe() as being (only?) "deemed
acceptable" has a bad connotation. In fact dev_err_probe() fulfills
three tasks:

 - handling of EPROBE_DEFER (even more than degrading to dev_dbg())
 - symbolic output of the error code
 - return err for compact error code paths

Advertise these better and claim the usage to be "fine" to get rid of
the bad connotation.

Acked-by: Rafael J. Wysocki 
Signed-off-by: Uwe Kleine-König 
Link: https://lore.kernel.org/r/20231215174540.2438601-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman

driver core: Enable fw_devlink=rpm by default

2023-12-07T02:35:26+00:00

fw_devlink=on has stabilized and is working correctly. Let's start using
device links created by fw_devlink to also enforce runtime PM ordering.

Signed-off-by: Saravana Kannan 
Link: https://lore.kernel.org/r/20231113220948.80089-1-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman

driver core: make device_is_dependent() static

2023-11-28T20:14:25+00:00

The function device_is_dependent() is only called by the driver core
internally and should not, at this time, be called by anyone else
outside of it, so mark it as static so as not to give driver authors the
wrong idea.

Cc: Saravana Kannan 
Acked-by: "Rafael J. Wysocki" 
Link: https://lore.kernel.org/r/2023112815-faculty-thud-add8@gregkh
Signed-off-by: Greg Kroah-Hartman