[SCSI] megaraid_sas: support for poll_mode_io (reduced interrupt)

Added module parameter "poll_mode_io" to support for "polling"
(reduced interrupt operation).  In this mode, IO completion interrupts
are delayed. At the end of initiating IOs, the driver schedules for
cmd completion if there are pending cmds.  A timer-based interrupt has
also been added to prevent IO completion from being delayed
indefinitely in the case that no new IOs are initiated.  Some
formatting issues in resume, suspend comment block also corrected

Signed-off-by: Bo Yang <bo.yang@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/scsi/megaraid/megaraid_sas.h b/drivers/scsi/megaraid/megaraid_sas.h
index c3575a304c6a..dcc66fc9c2cb 100644
--- a/drivers/scsi/megaraid/megaraid_sas.h
+++ b/drivers/scsi/megaraid/megaraid_sas.h
@@ -572,6 +572,7 @@ struct megasas_ctrl_info {
 
 #define MFI_OB_INTR_STATUS_MASK                 0x00000002
 #define MFI_POLL_TIMEOUT_SECS                   60
+#define MEGASAS_COMPLETION_TIMER_INTERVAL      (HZ/10)
 
 #define MFI_REPLY_1078_MESSAGE_INTERRUPT        0x80000000
 
@@ -1111,6 +1112,8 @@ struct megasas_instance {
 
         u8 flag;
         unsigned long last_time;
+
+        struct timer_list io_completion_timer;
 };
 
 #define MEGASAS_IS_LOGICAL(scp)                                         \