[SCSI] qla4xxx: Throttle active IOCBs to firmware limits

Problem:
QLA4xxx firmware may assert if given more IOCBs than it can handle.

Solution:
The driver was updated to throttle the number of active IOCBs based
on the total number of IOCB buffers received from get_firmware_status
mbx_sts[2].

Signed-off-by: Karen Higgins <karen.higgins@qlogic.com>
Signed-off-by: Vikas Chaudhary <vikas.chaudhary@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

3 files changed, 21 insertions, 3 deletions

diff --git a/drivers/scsi/qla4xxx/ql4_def.h b/drivers/scsi/qla4xxx/ql4_def.h
index 8f4193766663..ad580625a477 100644
--- a/drivers/scsi/qla4xxx/ql4_def.h
+++ b/drivers/scsi/qla4xxx/ql4_def.h
@@ -136,6 +136,7 @@
 #define RESPONSE_QUEUE_DEPTH            64
 #define QUEUE_SIZE                      64
 #define DMA_BUFFER_SIZE                 512
+#define IOCB_HIWAT_CUSHION              4
 
 /*
  * Misc
@@ -540,6 +541,7 @@ struct scsi_qla_host {
         uint32_t tot_ddbs;
 
         uint16_t iocb_cnt;
+        uint16_t iocb_hiwat;
 
         /* SRB cache. */
 #define SRB_MIN_REQ     128
diff --git a/drivers/scsi/qla4xxx/ql4_iocb.c b/drivers/scsi/qla4xxx/ql4_iocb.c
index f48f37a281d1..14fec976f634 100644
--- a/drivers/scsi/qla4xxx/ql4_iocb.c
+++ b/drivers/scsi/qla4xxx/ql4_iocb.c
@@ -316,7 +316,7 @@ int qla4xxx_send_command_to_isp(struct scsi_qla_host *ha, struct srb * srb)
                 goto queuing_error;
 
         /* total iocbs active */
-        if ((ha->iocb_cnt + req_cnt) >= REQUEST_QUEUE_DEPTH)
+        if ((ha->iocb_cnt + req_cnt) >= ha->iocb_hiwat)
                 goto queuing_error;
 
         /* Build command packet */
diff --git a/drivers/scsi/qla4xxx/ql4_mbx.c b/drivers/scsi/qla4xxx/ql4_mbx.c
index 1c57c227c808..81e738d61ec0 100644
--- a/drivers/scsi/qla4xxx/ql4_mbx.c
+++ b/drivers/scsi/qla4xxx/ql4_mbx.c
@@ -697,8 +697,24 @@ int qla4xxx_get_firmware_status(struct scsi_qla_host * ha)
                 return QLA_ERROR;
         }
 
-        ql4_printk(KERN_INFO, ha, "%ld firmware IOCBs available (%d).\n",
-            ha->host_no, mbox_sts[2]);
+        /* High-water mark of IOCBs */
+        ha->iocb_hiwat = mbox_sts[2];
+        DEBUG2(ql4_printk(KERN_INFO, ha,
+                          "%s: firmware IOCBs available = %d\n", __func__,
+                          ha->iocb_hiwat));
+
+        if (ha->iocb_hiwat > IOCB_HIWAT_CUSHION)
+                ha->iocb_hiwat -= IOCB_HIWAT_CUSHION;
+
+        /* Ideally, we should not enter this code, as the # of firmware
+         * IOCBs is hard-coded in the firmware. We set a default
+         * iocb_hiwat here just in case */
+        if (ha->iocb_hiwat == 0) {
+                ha->iocb_hiwat = REQUEST_QUEUE_DEPTH / 4;
+                DEBUG2(ql4_printk(KERN_WARNING, ha,
+                                  "%s: Setting IOCB's to = %d\n", __func__,
+                                  ha->iocb_hiwat));
+        }
 
         return QLA_SUCCESS;
 }