[SCSI] aacraid: 17 element sg performance update

Received From Mark Salyzyn.

The Jaguar and Corsair class of adapters (2410, 2810, 2610, 21610, CERC)
perform better (about 10% better read performance, write performance
neutral) with current Firmware if the OS limits the number of scatter
gather elements to 17 per request.
Signed-off-by: Mark Haverkamp <markh@osdl.org>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/aacraid/aacraid.h

@@ -531,6 +531,13 @@ struct aac_driver_ident
  */
 #define AAC_QUIRK_MASTER 0x0008
 
+/*
+ * Some adapter firmware perform poorly when it must split up scatter gathers
+ * in order to deal with the limits of the underlying CHIM. This limit in this
+ * class of adapters is 17 scatter gather elements.
+ */
+#define AAC_QUIRK_17SG	0x0010
+
 /*
  *	The adapter interface specs all queues to be located in the same
  *	physically contigous block. The host structure that defines the

drivers/scsi/aacraid/linit.c

@@ -200,10 +200,10 @@ static struct aac_driver_ident aac_drivers[] = {
 	{ aac_rkt_init, "aacraid",  "ADAPTEC ", "Callisto        ", 2, AAC_QUIRK_MASTER }, /* Jupiter Platform */
 	{ aac_rx_init, "aacraid",  "ADAPTEC ", "ASR-2020SA       ", 1 }, /* ASR-2020SA SATA PCI-X ZCR (Skyhawk) */
 	{ aac_rx_init, "aacraid",  "ADAPTEC ", "ASR-2025SA       ", 1 }, /* ASR-2025SA SATA SO-DIMM PCI-X ZCR (Terminator) */
-	{ aac_rx_init, "aacraid",  "ADAPTEC ", "AAR-2410SA SATA ", 1 }, /* AAR-2410SA PCI SATA 4ch (Jaguar II) */
-	{ aac_rx_init, "aacraid",  "DELL    ", "CERC SR2        ", 1 }, /* CERC SATA RAID 2 PCI SATA 6ch (DellCorsair) */
-	{ aac_rx_init, "aacraid",  "ADAPTEC ", "AAR-2810SA SATA ", 1 }, /* AAR-2810SA PCI SATA 8ch (Corsair-8) */
-	{ aac_rx_init, "aacraid",  "ADAPTEC ", "AAR-21610SA SATA", 1 }, /* AAR-21610SA PCI SATA 16ch (Corsair-16) */
+	{ aac_rx_init, "aacraid",  "ADAPTEC ", "AAR-2410SA SATA ", 1, AAC_QUIRK_17SG }, /* AAR-2410SA PCI SATA 4ch (Jaguar II) */
+	{ aac_rx_init, "aacraid",  "DELL    ", "CERC SR2        ", 1, AAC_QUIRK_17SG }, /* CERC SATA RAID 2 PCI SATA 6ch (DellCorsair) */
+	{ aac_rx_init, "aacraid",  "ADAPTEC ", "AAR-2810SA SATA ", 1, AAC_QUIRK_17SG }, /* AAR-2810SA PCI SATA 8ch (Corsair-8) */
+	{ aac_rx_init, "aacraid",  "ADAPTEC ", "AAR-21610SA SATA", 1, AAC_QUIRK_17SG }, /* AAR-21610SA PCI SATA 16ch (Corsair-16) */
 	{ aac_rx_init, "aacraid",  "ADAPTEC ", "ASR-2026ZCR     ", 1 }, /* ESD SO-DIMM PCI-X SATA ZCR (Prowler) */
 	{ aac_rx_init, "aacraid",  "ADAPTEC ", "AAR-2610SA      ", 1 }, /* SATA 6Ch (Bearcat) */
 	{ aac_rx_init, "aacraid",  "ADAPTEC ", "ASR-2240S       ", 1 }, /* ASR-2240S (SabreExpress) */
@@ -853,6 +853,13 @@ static int __devinit aac_probe_one(struct pci_dev *pdev,
  		  = (aac->scsi_host_ptr->sg_tablesize * 8) + 112;
  	}
 
+ 	if ((aac_drivers[index].quirks & AAC_QUIRK_17SG) &&
+			(aac->scsi_host_ptr->sg_tablesize > 17)) {
+ 		aac->scsi_host_ptr->sg_tablesize = 17;
+ 		aac->scsi_host_ptr->max_sectors
+ 		  = (aac->scsi_host_ptr->sg_tablesize * 8) + 112;
+ 	}
+
 	/*
 	 * Firware printf works only with older firmware.
 	 */