hpsa: avoid unnecessary readl on every command submission

for controllers which support either of the ioaccel transport methods.

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Reviewed-by: Mike Miller <michael.miller@canonical.com>
Reviewed-by: Joe Handzik <joseph.t.handzik@hp.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

2 files changed, 21 insertions, 1 deletions

diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
index 3b70e66838ad..3e501df02e35 100644
--- a/drivers/scsi/hpsa.c
+++ b/drivers/scsi/hpsa.c
@@ -7330,6 +7330,13 @@ static void hpsa_enter_performant_mode(struct ctlr_info *h, u32 trans_support)
          * 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);
diff --git a/drivers/scsi/hpsa.h b/drivers/scsi/hpsa.h
index 6da9a9f4b749..0a5d91c4ded8 100644
--- a/drivers/scsi/hpsa.h
+++ b/drivers/scsi/hpsa.h
@@ -346,6 +346,12 @@ static void SA5_submit_command(struct ctlr_info *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)
 {
@@ -353,7 +359,6 @@ static void SA5_submit_command_ioaccel2(struct ctlr_info *h,
                 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);
 }
 
 /*
@@ -564,6 +569,14 @@ static struct access_method SA5_performant_access = {
         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,
+        SA5_performant_completed,
+};
+
 struct board_type {
         u32     board_id;
         char    *product_name;