scsi: cxlflash: Track pending scsi commands in each hardware queue

Currently, there is no book keeping of the pending scsi commands in the
cxlflash driver. This lack of tracking in-flight requests is too
restrictive and requires a heavy-hammer reset each time an adapter error is
encountered. Additionally, it does not allow for commands to be properly
retried.

In order to avoid this problem and to better handle error path command
cleanup, introduce a linked list for each hardware queue that tracks
pending commands.
Signed-off-by: Uma Krishnan <ukrishn@linux.vnet.ibm.com>
Acked-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/cxlflash/common.h

@@ -158,6 +158,7 @@ struct afu_cmd {
 	u32 hwq_index;
 
 	u8 cmd_tmf:1;
+	struct list_head list;	/* Pending commands link */
 
 	/* As per the SISLITE spec the IOARCB EA has to be 16-byte aligned.
 	 * However for performance reasons the IOARCB/IOASA should be
@@ -193,6 +194,7 @@ struct hwq {
 	struct sisl_ctrl_map __iomem *ctrl_map;		/* MC control map */
 	ctx_hndl_t ctx_hndl;	/* master's context handle */
 	u32 index;		/* Index of this hwq */
+	struct list_head pending_cmds;	/* Commands pending completion */
 
 	atomic_t hsq_credits;
 	spinlock_t hsq_slock;	/* Hardware send queue lock */

drivers/scsi/cxlflash/main.c

@@ -162,8 +162,13 @@ static void cmd_complete(struct afu_cmd *cmd)
 	struct afu *afu = cmd->parent;
 	struct cxlflash_cfg *cfg = afu->parent;
 	struct device *dev = &cfg->dev->dev;
+	struct hwq *hwq = get_hwq(afu, cmd->hwq_index);
 	bool cmd_is_tmf;
 
+	spin_lock_irqsave(&hwq->hsq_slock, lock_flags);
+	list_del(&cmd->list);
+	spin_unlock_irqrestore(&hwq->hsq_slock, lock_flags);
+
 	if (cmd->scp) {
 		scp = cmd->scp;
 		if (unlikely(cmd->sa.ioasc))
@@ -279,6 +284,7 @@ static int send_cmd_ioarrin(struct afu *afu, struct afu_cmd *cmd)
 		hwq->room = room - 1;
 	}
 
+	list_add(&cmd->list, &hwq->pending_cmds);
 	writeq_be((u64)&cmd->rcb, &hwq->host_map->ioarrin);
 out:
 	spin_unlock_irqrestore(&hwq->hsq_slock, lock_flags);
@@ -319,6 +325,8 @@ static int send_cmd_sq(struct afu *afu, struct afu_cmd *cmd)
 		hwq->hsq_curr++;
 	else
 		hwq->hsq_curr = hwq->hsq_start;
+
+	list_add(&cmd->list, &hwq->pending_cmds);
 	writeq_be((u64)hwq->hsq_curr, &hwq->host_map->sq_tail);
 
 	spin_unlock_irqrestore(&hwq->hsq_slock, lock_flags);
@@ -1840,6 +1848,7 @@ static int init_mc(struct cxlflash_cfg *cfg, u32 index)
 
 	hwq->afu = cfg->afu;
 	hwq->index = index;
+	INIT_LIST_HEAD(&hwq->pending_cmds);
 
 	if (index == PRIMARY_HWQ)
 		ctx = cxl_get_context(cfg->dev);