opal/hmi: Don't retry TOD recovery if it is already in failed state.

On TOD failure, all cores/thread receives HMI and very first thread that
gets interrupt fixes the TOD where as others just resets the respective
HMER error bit and return. But when TOD is unrecoverable, all the threads
try to do TOD recovery one by one causing threads to spend more time inside
opal. Set a global flag when TOD is unrecoverable so that rest of the
threads go back to linux immediately avoiding lock ups in system
reboot/panic path.

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

hw/chiptod.c

@@ -227,6 +227,7 @@ static uint64_t base_tfmr;
  * take all of them for RAS cases.
  */
 static struct lock chiptod_lock = LOCK_UNLOCKED;
+static bool chiptod_unrecoverable;
 
 static void _chiptod_cache_tod_regs(int32_t chip_id)
 {
@@ -1234,7 +1235,6 @@ static void chiptod_topology_switch_complete(void)
 static int chiptod_start_tod(void)
 {
 	struct proc_chip *chip = NULL;
-	int rc = 1;
 
 	/*  Do a topology switch if required. */
 	if (is_topology_switch_required()) {
@@ -1257,14 +1257,14 @@ static int chiptod_start_tod(void)
 		if (!chiptod_backup_valid()) {
 			prerror("Backup master is not enabled. "
 				"Can not do a topology switch.\n");
-			return 0;
+			goto error_out;
 		}
 
 		chiptod_stop_slave_tods();
 
 		if (xscom_write(mchip, TOD_TTYPE_1, PPC_BIT(0))) {
 			prerror("XSCOM error switching primary/secondary\n");
-			return 0;
+			goto error_out;
 		}
 
 		/* Update topology info. */
@@ -1278,7 +1278,7 @@ static int chiptod_start_tod(void)
 		 */
 		if (!chiptod_master_running()) {
 			prerror("TOD is not running on new master.\n");
-			return 0;
+			goto error_out;
 		}
 
 		/*
@@ -1289,7 +1289,7 @@ static int chiptod_start_tod(void)
 		 */
 		if (xscom_writeme(TOD_TTYPE_2, PPC_BIT(0))) {
 			prerror("XSCOM error enabling steppers\n");
-			return 0;
+			goto error_out;
 		}
 
 		chiptod_topology_switch_complete();
@@ -1314,7 +1314,7 @@ static int chiptod_start_tod(void)
 	/* Switch local chiptod to "Not Set" state */
 	if (xscom_writeme(TOD_LOAD_TOD_MOD, PPC_BIT(0))) {
 		prerror("XSCOM error sending LOAD_TOD_MOD\n");
-		return 0;
+		goto error_out;
 	}
 
 	/*
@@ -1323,16 +1323,20 @@ static int chiptod_start_tod(void)
 	 */
 	if (xscom_writeme(TOD_TTYPE_3, PPC_BIT(0))) {
 		prerror("XSCOM error sending TTYPE_3\n");
-		return 0;
+		goto error_out;
 	}
 
 	/* Check if chip TOD is running. */
 	if (!chiptod_poll_running())
-		rc = 0;
+		goto error_out;
 
 	/* Restore the ttype4_mode. */
 	chiptod_set_ttype4_mode(chip, false);
-	return rc;
+	return 1;
+
+error_out:
+	chiptod_unrecoverable = true;
+	return 0;
 }
 
 static bool tfmr_recover_tb_errors(uint64_t tfmr)
@@ -1533,6 +1537,15 @@ int chiptod_recover_tb_errors(bool *out_resynced)
 
 	lock(&chiptod_lock);
 
+	/*
+	 * Return if TOD is unrecoverable.
+	 * The previous attempt to recover TOD has been failed.
+	 */
+	if (chiptod_unrecoverable) {
+		rc = 0;
+		goto error_out;
+	}
+
 	/* Get fresh copy of TFMR */
 	tfmr = mfspr(SPR_TFMR);