scsi: ufs: Fix broken task management command implementation

Currently, sending Task Management (TM) command to the card might
be broken in some scenarios as listed below:

Problem: If there are more than 8 TM commands the implementation
         returns error to the caller.
Fix:     Wait for one of the slots to be emptied and send the command.

Problem: Sometimes it is necessary for the caller to know the TM service
         response code to determine the task status.
Fix:     Propogate the service response to the caller.

Problem: If the TM command times out no proper error recovery is
         implemented.
Fix:     Clear the command in the controller door-bell register, so that
         further commands for the same slot don't fail.

Problem: While preparing the TM command descriptor, the task tag used
         should be unique across SCSI/NOP/QUERY/TM commands and not the
	 task tag of the command which the TM command is trying to manage.
Fix:     Use a unique task tag instead of task tag of SCSI command.

Problem: Since the TM command involves H/W communication, abruptly ending
         the request on kill interrupt signal might cause h/w malfunction.
Fix:     Wait for hardware completion interrupt with TASK_UNINTERRUPTIBLE
         set.

Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>
Reviewed-by: Yaniv Gardi <ygardi@codeaurora.org>
Tested-by: Dolev Raviv <draviv@codeaurora.org>
Acked-by: Vinayak Holikatti <vinholikatti@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index 767ee9ebfaf1..84d09d1ae881 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -174,7 +174,9 @@ struct ufs_dev_cmd {
  * @irq: Irq number of the controller
  * @active_uic_cmd: handle of active UIC command
  * @uic_cmd_mutex: mutex for uic command
- * @ufshcd_tm_wait_queue: wait queue for task management
+ * @tm_wq: wait queue for task management
+ * @tm_tag_wq: wait queue for free task management slots
+ * @tm_slots_in_use: bit map of task management request slots in use
  * @pwr_done: completion for power mode change
  * @tm_condition: condition variable for task management
  * @ufshcd_state: UFSHCD states
@@ -217,8 +219,10 @@ struct ufs_hba {
 	struct uic_command *active_uic_cmd;
 	struct mutex uic_cmd_mutex;
 
-	wait_queue_head_t ufshcd_tm_wait_queue;
+	wait_queue_head_t tm_wq;
+	wait_queue_head_t tm_tag_wq;
 	unsigned long tm_condition;
+	unsigned long tm_slots_in_use;
 
 	struct completion *pwr_done;