This patch will add capability in driver to tell firmware that it can throttle 
IOs in case Controller's Queue depth is downgraded post OFU
(Online firmware upgrade). This feature will ensure firmware can be downgraded 
from higher queue depth to lower queue depth without needing system reboot.
Added throttling code in IO path of driver, in case OS tries to send more IOs 
than post OFU firmware's queue depth.

I have accomodated Tomas' comments provided on last time sent patch- removed 
the un-necessary code of throttling of IOs against can_queue inside
function- megasas_build_and_issue_cmd_fusion() as SCSI mid layer will anyways 
does this.

Signed-off-by: Sumit Saxena <sumit.sax...@avagotech.com>
Signed-off-by: Kashyap Desai <kashyap.de...@avagotech.com>
---
 drivers/scsi/megaraid/megaraid_sas.h        | 6 ++++--
 drivers/scsi/megaraid/megaraid_sas_fusion.c | 1 +
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/megaraid/megaraid_sas.h 
b/drivers/scsi/megaraid/megaraid_sas.h
index 2a2f491..c8d25a7 100644
--- a/drivers/scsi/megaraid/megaraid_sas.h
+++ b/drivers/scsi/megaraid/megaraid_sas.h
@@ -1537,7 +1537,8 @@ union megasas_sgl_frame {
 typedef union _MFI_CAPABILITIES {
        struct {
 #if   defined(__BIG_ENDIAN_BITFIELD)
-               u32     reserved:21;
+               u32     reserved:20;
+               u32     support_qd_throttling:1;
                u32     support_fp_rlbypass:1;
                u32     support_vfid_in_ioframe:1;
                u32     support_ext_io_size:1;
@@ -1561,7 +1562,8 @@ typedef union _MFI_CAPABILITIES {
                u32     support_ext_io_size:1;
                u32     support_vfid_in_ioframe:1;
                u32     support_fp_rlbypass:1;
-               u32     reserved:21;
+               u32     support_qd_throttling:1;
+               u32     reserved:20;
 #endif
        } mfi_capabilities;
        __le32          reg;
diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.c 
b/drivers/scsi/megaraid/megaraid_sas_fusion.c
index 6b8547c..2c4912f 100644
--- a/drivers/scsi/megaraid/megaraid_sas_fusion.c
+++ b/drivers/scsi/megaraid/megaraid_sas_fusion.c
@@ -803,6 +803,7 @@ megasas_ioc_init_fusion(struct megasas_instance *instance)
        if (!dual_qdepth_disable)
                drv_ops->mfi_capabilities.support_ext_queue_depth = 1;
 
+       drv_ops->mfi_capabilities.support_qd_throttling = 1;
        /* Convert capability to LE32 */
        cpu_to_le32s((u32 *)&init_frame->driver_operations.mfi_capabilities);
 
-- 
1.8.3.1

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