[SCSI] hpsa: allow driver to put controller in either simple or performant mode

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

2 files changed, 13 insertions, 0 deletions

diff --git a/Documentation/scsi/hpsa.txt b/Documentation/scsi/hpsa.txt
index dca658362cbf..b14e6ee00a95 100644
--- a/Documentation/scsi/hpsa.txt
+++ b/Documentation/scsi/hpsa.txt
@@ -28,6 +28,12 @@ boot parameter "hpsa_allow_any=1" is specified, however these are not tested
 nor supported by HP with this driver.  For older Smart Arrays, the cciss
 driver should still be used.
 
+The "hpsa_simple_mode=1" boot parameter may be used to prevent the driver from
+putting the controller into "performant" mode.  The difference is that with simple
+mode, each command completion requires an interrupt, while with "performant mode"
+(the default, and ordinarily better performing) it is possible to have multiple
+command completions indicated by a single interrupt.
+
 HPSA specific entries in /sys
 -----------------------------
 
diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
index 4fb62c2aac05..10076f1868e0 100644
--- a/drivers/scsi/hpsa.c
+++ b/drivers/scsi/hpsa.c
@@ -74,6 +74,10 @@ static int hpsa_allow_any;
 module_param(hpsa_allow_any, int, S_IRUGO|S_IWUSR);
 MODULE_PARM_DESC(hpsa_allow_any,
                 "Allow hpsa driver to access unknown HP Smart Array hardware");
+static int hpsa_simple_mode;
+module_param(hpsa_simple_mode, int, S_IRUGO|S_IWUSR);
+MODULE_PARM_DESC(hpsa_simple_mode,
+        "Use 'simple mode' rather than 'performant mode'");
 
 /* define the PCI info for the cards we can control */
 static const struct pci_device_id hpsa_pci_device_id[] = {
@@ -4038,6 +4042,9 @@ static __devinit void hpsa_put_ctlr_into_performant_mode(struct ctlr_info *h)
 {
         u32 trans_support;
 
+        if (hpsa_simple_mode)
+                return;
+
         trans_support = readl(&(h->cfgtable->TransportSupport));
         if (!(trans_support & PERFORMANT_MODE))
                 return;