i3c: master: Ensure Hot-Join operations are stopped on shutdown

System shutdown invokes each device's bus shutdown callback to quiesce
hardware, but the I3C bus type does not currently implement one.  As a
result, on shutdown the controller's Hot-Join work and any in-flight
i3c_master_do_daa() can keep running (or be newly triggered) while the
rest of the system is being torn down.

A similar window exists at i3c_master_unregister() time: cancel_work_sync()
on hj_work prevents queued work from completing, but does not stop a
fresh Hot-Join IBI from re-queueing the worker, nor a concurrent sysfs
writer from toggling Hot-Join via i3c_set_hotjoin().

Introduce a single "shutting down" gate in the I3C core, set under the
bus maintenance lock so it is observed by any in-progress DAA path
before pending work is cancelled.  Install an i3c_bus_type shutdown
callback that engages this gate for master devices during system
shutdown, and use the same gate in i3c_master_unregister() so both
paths get identical guarantees.

Once the gate is engaged, the Hot-Join worker, i3c_master_do_daa_ext()
and i3c_set_hotjoin() all bail out cleanly, so Hot-Join IBIs that race
with shutdown become no-ops, direct DAA callers see -ENODEV, and sysfs
writers can no longer re-enable Hot-Join through ops->enable_hotjoin()
while the controller is going away.

No functional change for the steady-state runtime path; the new checks
only take effect once the controller has been marked as shutting down.

Note, this patch depends on patch "i3c: master: Consolidate Hot-Join DAA
work in the core".

Fixes: 3a379bbcea0af ("i3c: Add core I3C infrastructure")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260608054312.10604-5-adrian.hunter@intel.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
index eb5c51608bd7..77e63082b06e 100644
--- a/include/linux/i3c/master.h
+++ b/include/linux/i3c/master.h
@@ -511,6 +511,7 @@ struct i3c_master_controller_ops {
  * @hotjoin: true if the master support hotjoin
  * @rpm_allowed: true if Runtime PM allowed
  * @rpm_ibi_allowed: true if IBI and Hot-Join allowed while runtime suspended
+ * @shutting_down: set to true when master begins shutdown or unregister
  * @boardinfo.i3c: list of I3C  boardinfo objects
  * @boardinfo.i2c: list of I2C boardinfo objects
  * @boardinfo: board-level information attached to devices connected on the bus
@@ -539,6 +540,7 @@ struct i3c_master_controller {
 	unsigned int hotjoin: 1;
 	unsigned int rpm_allowed: 1;
 	unsigned int rpm_ibi_allowed: 1;
+	bool shutting_down;
 	struct {
 		struct list_head i3c;
 		struct list_head i2c;