[PATCH] Work around aacraid FW problem

If you have a 4gig or greater system, some versions of aacraid firmware
have problems if you set HostPhysMemPages >= 0x100000.  This can
potentially cause data corruption.  If you have 4gig or greater memory,
this patch sets the HostPhysMemPages to something that the firmware can
deal with.

drivers/scsi/aacraid/aacraid.h

@@ -14,6 +14,8 @@
 #define AAC_MAX_TARGET (MAXIMUM_NUM_CONTAINERS+1)
 #define AAC_MAX_LUN	(8)
 
+#define AAC_MAX_HOSTPHYSMEMPAGES (0xfffff)
+
 /*
  * These macros convert from physical channels to virtual channels
  */

drivers/scsi/aacraid/comminit.c

@@ -92,7 +92,21 @@ static int aac_alloc_comm(struct aac_dev *dev, void **commaddr, unsigned long co
 	init->AdapterFibsPhysicalAddress = cpu_to_le32((u32)phys);
 	init->AdapterFibsSize = cpu_to_le32(fibsize);
 	init->AdapterFibAlign = cpu_to_le32(sizeof(struct hw_fib));
-	init->HostPhysMemPages = cpu_to_le32(num_physpages);		// number of 4k pages of host physical memory
+	/* 
+	 * number of 4k pages of host physical memory. The aacraid fw needs
+	 * this number to be less than 4gb worth of pages. num_physpages is in
+	 * system page units. New firmware doesn't have any issues with the
+	 * mapping system, but older Firmware did, and had *troubles* dealing
+	 * with the math overloading past 32 bits, thus we must limit this
+	 * field.
+	 */
+	if ((num_physpages << (PAGE_SHIFT - 12)) <= AAC_MAX_HOSTPHYSMEMPAGES) {
+		init->HostPhysMemPages = 
+			cpu_to_le32(num_physpages << (PAGE_SHIFT-12));
+	} else {
+		init->HostPhysMemPages = cpu_to_le32(AAC_MAX_HOSTPHYSMEMPAGES);
+	}
+
 
 	/*
 	 * Increment the base address by the amount already used