sata_nv: Use notifier for completion checks

The hardware provides us a notifier register that indicates what command
tags have completed. Use this to determine which CPBs to check, rather
than blindly checking all active CPBs. This should provide a minor
performance win, since if the controller has touched some of these
incomplete CPBs, accessing them will likely result in a cache miss.

Signed-off-by: Robert Hancock <hancockr@shaw.ca>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/ata/sata_nv.c

@@ -854,22 +854,14 @@ static irqreturn_t nv_adma_interrupt(int irq, void *dev_instance)
 
 			if (status & (NV_ADMA_STAT_DONE |
 				      NV_ADMA_STAT_CPBERR)) {
-				/** Check CPBs for completed commands */
-
-				if (ata_tag_valid(ap->active_tag)) {
-					/* Non-NCQ command */
-					nv_adma_check_cpb(ap, ap->active_tag,
-						notifier_error & (1 << ap->active_tag));
-				} else {
+				u32 check_commands = notifier | notifier_error;
 				int pos, error = 0;
-					u32 active = ap->sactive;
-
-					while ((pos = ffs(active)) && !error) {
+				/** Check CPBs for completed commands */
+				while ((pos = ffs(check_commands)) && !error) {
 					pos--;
 					error = nv_adma_check_cpb(ap, pos,
 						notifier_error & (1 << pos) );
-						active &= ~(1 << pos );
-					}
+					check_commands &= ~(1 << pos );
 				}
 			}
 		}