linux-kernel - [PATCH 4/5] sata_nv: Use notifier for completion checks

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Date:	Mon, 19 Feb 2007 19:03:08 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-ide@...r.kernel.org, Jeff Garzik <jeff@...zik.org>,
	Andrew Morton <akpm@...l.org>
Subject: [PATCH 4/5] 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@...w.ca>

--- linux-2.6.20-git6edit/drivers/ata/sata_nv.c	2007-02-15 22:36:02.000000000 -0600
+++ linux-2.6.20-git6edit/drivers/ata/sata_nv.c.delayandfixes	2007-02-19 17:00:14.000000000 -0600
@@ -853,22 +854,14 @@ static irqreturn_t nv_adma_interrupt(int
 
 			if (status & (NV_ADMA_STAT_DONE |
 				      NV_ADMA_STAT_CPBERR)) {
+				u32 check_commands = notifier | notifier_error;
+				int pos, error = 0;
 				/** 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 {
-					int pos, error = 0;
-					u32 active = ap->sactive;
-
-					while ((pos = ffs(active)) && !error) {
-						pos--;
-						error = nv_adma_check_cpb(ap, pos,
-							notifier_error & (1 << pos) );
-						active &= ~(1 << pos );
-					}
+				while ((pos = ffs(check_commands)) && !error) {
+					pos--;
+					error = nv_adma_check_cpb(ap, pos,
+						notifier_error & (1 << pos) );
+					check_commands &= ~(1 << pos );
 				}
 			}
 		}

-
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