scsi: hisi_sas: Change common allocation mode of device id

To reduce possibility of hitting unknown SoC bugs and aid debugging and
test, change allocation mode of device id from last used device id instead
of lowest available index.
Signed-off-by: NXiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: NJohn Garry <john.garry@huawei.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/hisi_sas/hisi_sas.h

@@ -275,6 +275,7 @@ struct hisi_hba {
 
 	int slot_index_count;
 	int last_slot_index;
+	int last_dev_id;
 	unsigned long *slot_index_tags;
 	unsigned long reject_stp_links_msk;
 

drivers/scsi/hisi_sas/hisi_sas_main.c

@@ -596,10 +596,12 @@ static struct hisi_sas_device *hisi_sas_alloc_dev(struct domain_device *device)
 	struct hisi_hba *hisi_hba = dev_to_hisi_hba(device);
 	struct hisi_sas_device *sas_dev = NULL;
 	unsigned long flags;
+	int last = hisi_hba->last_dev_id;
+	int first = (hisi_hba->last_dev_id + 1) % HISI_SAS_MAX_DEVICES;
 	int i;
 
 	spin_lock_irqsave(&hisi_hba->lock, flags);
-	for (i = 0; i < HISI_SAS_MAX_DEVICES; i++) {
+	for (i = first; i != last; i %= HISI_SAS_MAX_DEVICES) {
 		if (hisi_hba->devices[i].dev_type == SAS_PHY_UNUSED) {
 			int queue = i % hisi_hba->queue_count;
 			struct hisi_sas_dq *dq = &hisi_hba->dq[queue];
@@ -614,7 +616,9 @@ static struct hisi_sas_device *hisi_sas_alloc_dev(struct domain_device *device)
 			INIT_LIST_HEAD(&hisi_hba->devices[i].list);
 			break;
 		}
+		i++;
 	}
+	hisi_hba->last_dev_id = i;
 	spin_unlock_irqrestore(&hisi_hba->lock, flags);
 
 	return sas_dev;