scsi: lpfc: Fix MDS diagnostics failure (Rx < Tx)

MDS diagnostics fail because of frame count mismatch.

Unavailability of SGL is the trigger for this issue. If ELS SGL is not
available to process MDS frame, IOCB is put in FCP txq but not attempted to
post afterwards. So, driver stops processing incoming frames as it runs out
of IOCB.  lpfc_drain_txq attempts to submit IOCBS that are queued in ELS
txq but MDS frames are posted to FCP WQ.

Attempt to submit IOCBs that are present in FCP txq when MDS loopback is
running.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

2 files changed, 17 insertions, 5 deletions

diff --git a/drivers/scsi/lpfc/lpfc_hbadisc.c b/drivers/scsi/lpfc/lpfc_hbadisc.c
index cf2cbaa241b9..2fef54fab86d 100644
--- a/drivers/scsi/lpfc/lpfc_hbadisc.c
+++ b/drivers/scsi/lpfc/lpfc_hbadisc.c
@@ -708,8 +708,7 @@ lpfc_work_done(struct lpfc_hba *phba)
                                                                 HA_RXMASK));
                         }
                 }
-                if ((phba->sli_rev == LPFC_SLI_REV4) &&
-                                 (!list_empty(&pring->txq)))
+                if (phba->sli_rev == LPFC_SLI_REV4)
                         lpfc_drain_txq(phba);
                 /*
                  * Turn on Ring interrupts
diff --git a/drivers/scsi/lpfc/lpfc_sli.c b/drivers/scsi/lpfc/lpfc_sli.c
index 6b709cd4140b..4b70d53acb72 100644
--- a/drivers/scsi/lpfc/lpfc_sli.c
+++ b/drivers/scsi/lpfc/lpfc_sli.c
@@ -19069,9 +19069,22 @@ lpfc_drain_txq(struct lpfc_hba *phba)
         struct lpfc_sglq *sglq;
         union lpfc_wqe128 wqe;
         uint32_t txq_cnt = 0;
+        struct lpfc_queue *wq;
 
-        pring = lpfc_phba_elsring(phba);
-        if (unlikely(!pring))
+        if (phba->link_flag & LS_MDS_LOOPBACK) {
+                /* MDS WQE are posted only to first WQ*/
+                wq = phba->sli4_hba.fcp_wq[0];
+                if (unlikely(!wq))
+                        return 0;
+                pring = wq->pring;
+        } else {
+                wq = phba->sli4_hba.els_wq;
+                if (unlikely(!wq))
+                        return 0;
+                pring = lpfc_phba_elsring(phba);
+        }
+
+        if (unlikely(!pring) || list_empty(&pring->txq))
                 return 0;
 
         spin_lock_irqsave(&pring->ring_lock, iflags);
@@ -19112,7 +19125,7 @@ lpfc_drain_txq(struct lpfc_hba *phba)
                         fail_msg = "to convert bpl to sgl";
                 else if (lpfc_sli4_iocb2wqe(phba, piocbq, &wqe))
                         fail_msg = "to convert iocb to wqe";
-                else if (lpfc_sli4_wq_put(phba->sli4_hba.els_wq, &wqe))
+                else if (lpfc_sli4_wq_put(wq, &wqe))
                         fail_msg = " - Wq is full";
                 else
                         lpfc_sli_ringtxcmpl_put(phba, pring, piocbq);