hpsa: avoid unnecessary readl on every command submission

for controllers which support either of the ioaccel transport methods.

Signed-off-by: Stephen M. Cameron <[e-mail]>
Reviewed-by: Mike Miller <[e-mail]>
Reviewed-by: Joe Handzik <[e-mail]>
Signed-off-by: Christoph Hellwig <[e-mail]>

drivers/scsi/hpsa.c

···
 	 * 10 = 6 s/g entry or 24k
 	 */
 
+	/* If the controller supports either ioaccel method then
+	 * we can also use the RAID stack submit path that does not
+	 * perform the superfluous readl() after each command submission.
+	 */
+	if (trans_support & (CFGTBL_Trans_io_accel1 | CFGTBL_Trans_io_accel2))
+		access = SA5_performant_access_no_read;
+
 	/* Controller spec: zero out this buffer. */
 	for (i = 0; i < h->nreply_queues; i++)
 		memset(h->reply_queue[i].head, 0, h->reply_queue_size);

drivers/scsi/hpsa.h

···
 	(void) readl(h->vaddr + SA5_SCRATCHPAD_OFFSET);
 }
 
+static void SA5_submit_command_no_read(struct ctlr_info *h,
+	struct CommandList *c)
+{
+	writel(c->busaddr, h->vaddr + SA5_REQUEST_PORT_OFFSET);
+}
+
 static void SA5_submit_command_ioaccel2(struct ctlr_info *h,
 	struct CommandList *c)
 {
···
 		writel(c->busaddr, h->vaddr + IOACCEL2_INBOUND_POSTQ_32);
 	else
 		writel(c->busaddr, h->vaddr + SA5_REQUEST_PORT_OFFSET);
-	(void) readl(h->vaddr + SA5_SCRATCHPAD_OFFSET);
 }
 
 /*
···
 
 static struct access_method SA5_performant_access = {
 	SA5_submit_command,
+	SA5_performant_intr_mask,
+	SA5_fifo_full,
+	SA5_performant_intr_pending,
+	SA5_performant_completed,
+};
+
+static struct access_method SA5_performant_access_no_read = {
+	SA5_submit_command_no_read,
 	SA5_performant_intr_mask,
 	SA5_fifo_full,
 	SA5_performant_intr_pending,