scsi: ibmvfc: Implement channel queue depth and event buffer accounting

Extend ibmvfc_queue, ibmvfc_event, and ibmvfc_event_pool to provide queue
depths for general I/O commands and reserved commands as well as proper
accounting of the free events of each type from the general event
pool. Further, calculate the negotiated max command limit with the VIOS at
NPIV login time as a function of the number of queues times their total
queue depth (general and reserved depths combined).

This does away with the legacy max_request value, and allows the driver to
better manage and track it resources.
Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Link: https://lore.kernel.org/r/20230921225435.3537728-3-tyreld@linux.ibm.comReviewed-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ibmvscsi/ibmvfc.h

@@ -27,6 +27,7 @@
 #define IBMVFC_ABORT_TIMEOUT		8
 #define IBMVFC_ABORT_WAIT_TIMEOUT	40
 #define IBMVFC_MAX_REQUESTS_DEFAULT	100
+#define IBMVFC_SCSI_QDEPTH		128
 
 #define IBMVFC_DEBUG			0
 #define IBMVFC_MAX_TARGETS		1024
@@ -57,6 +58,8 @@
  * 2 for each discovery thread
  */
 #define IBMVFC_NUM_INTERNAL_REQ	(1 + 1 + 1 + 2 + (disc_threads * 2))
+/* Reserved suset of events for cancelling channelized IO commands */
+#define IBMVFC_NUM_INTERNAL_SUBQ_REQ 4
 
 #define IBMVFC_MAD_SUCCESS		0x00
 #define IBMVFC_MAD_NOT_SUPPORTED	0xF1
@@ -758,6 +761,7 @@ struct ibmvfc_event {
 	struct completion *eh_comp;
 	struct timer_list timer;
 	u16 hwq;
+	u8 reserved;
 };
 
 /* a pool of event structs for use */
@@ -793,6 +797,11 @@ struct ibmvfc_queue {
 	struct ibmvfc_event_pool evt_pool;
 	struct list_head sent;
 	struct list_head free;
+	u16 total_depth;
+	u16 evt_depth;
+	u16 reserved_depth;
+	u16 evt_free;
+	u16 reserved_free;
 	spinlock_t l_lock;
 
 	union ibmvfc_iu cancel_rsp;