scsi: lpfc: Cap CMF read bytes to MBPI

Ensure read bytes data does not go over MBPI for CMF timer intervals that
are purposely shortened.

Link: https://lore.kernel.org/r/20211204002644.116455-8-jsmart2021@gmail.com
Co-developed-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc.h

@@ -1028,7 +1028,7 @@ struct lpfc_hba {
 					 */
 #define HBA_PCI_ERR		0x80000 /* The PCI slot is offline */
 #define HBA_FLOGI_ISSUED	0x100000 /* FLOGI was issued */
-#define HBA_CGN_RSVD1		0x200000 /* Reserved CGN flag */
+#define HBA_SHORT_CMF		0x200000 /* shorter CMF timer routine */
 #define HBA_CGN_DAY_WRAP	0x400000 /* HBA Congestion info day wraps */
 #define HBA_DEFER_FLOGI		0x800000 /* Defer FLOGI till read_sparm cmpl */
 #define HBA_SETUP		0x1000000 /* Signifies HBA setup is completed */

drivers/scsi/lpfc/lpfc_init.c

@@ -6004,8 +6004,13 @@ lpfc_cmf_timer(struct hrtimer *timer)
 		if (ms && ms < LPFC_CMF_INTERVAL) {
 			cnt = div_u64(total, ms); /* bytes per ms */
 			cnt *= LPFC_CMF_INTERVAL; /* what total should be */
-			if (cnt > mbpi)
+
+			/* If the timeout is scheduled to be shorter,
+			 * this value may skew the data, so cap it at mbpi.
+			 */
+			if ((phba->hba_flag & HBA_SHORT_CMF) && cnt > mbpi)
 				cnt = mbpi;
+
 			extra = cnt - total;
 		}
 		lpfc_issue_cmf_sync_wqe(phba, LPFC_CMF_INTERVAL, total + extra);
@@ -6088,6 +6093,8 @@ lpfc_cmf_timer(struct hrtimer *timer)
 	/* Each minute save Fabric and Driver congestion information */
 	lpfc_cgn_save_evt_cnt(phba);
 
+	phba->hba_flag &= ~HBA_SHORT_CMF;
+
 	/* Since we need to call lpfc_cgn_save_evt_cnt every minute, on the
 	 * minute, adjust our next timer interval, if needed, to ensure a
 	 * 1 minute granularity when we get the next timer interrupt.
@@ -6098,6 +6105,8 @@ lpfc_cmf_timer(struct hrtimer *timer)
 						  jiffies);
 		if (timer_interval <= 0)
 			timer_interval = LPFC_CMF_INTERVAL;
+		else
+			phba->hba_flag |= HBA_SHORT_CMF;
 
 		/* If we adjust timer_interval, max_bytes_per_interval
 		 * needs to be adjusted as well.