hba->outstanding_tasks, which is read under host_lock spinlock, tells the
interrupt handler what task management tags are in use by the driver. The
doorbell register bits indicate which tags are in use by the hardware. A
doorbell bit that is 0 is because the bit has yet to be set by the driver,
or because the task is complete. It is only possible to disambiguate the 2
cases, if reading/writing the doorbell register is synchronized with
reading/writing hba->outstanding_tasks.
For that reason, reading REG_UTP_TASK_REQ_DOOR_BELL must be done under
spinlock.
Link: https://lore.kernel.org/r/20211108064815.569494-3-adrian.hunter@intel.com
Fixes: f5ef336fd2 ("scsi: ufs: core: Fix task management completion")
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
5cb37a2635