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From: Alexander Motin <mav@FreeBSD.org>
Date: Mon, 25 Mar 2013 13:58:18 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r248704 - head/sys/dev/ahci
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Author: mav
Date: Mon Mar 25 13:58:17 2013
New Revision: 248704
URL: http://svnweb.freebsd.org/changeset/base/248704

Log:
  Read Asynchronous Notification statuses only if Port Multiplier or ATAPI
  device are connected. ATA disks are not using ANs, while the extra register
  read operation is quite expensive.

Modified:
  head/sys/dev/ahci/ahci.c

Modified: head/sys/dev/ahci/ahci.c
==============================================================================
--- head/sys/dev/ahci/ahci.c	Mon Mar 25 13:33:06 2013	(r248703)
+++ head/sys/dev/ahci/ahci.c	Mon Mar 25 13:58:17 2013	(r248704)
@@ -1466,7 +1466,8 @@ ahci_ch_intr(void *data)
 	if (ch->numrslots != ch->numtslots)
 		cstatus |= ATA_INL(ch->r_mem, AHCI_P_CI);
 	/* Read SNTF in one of possible ways. */
-	if (istatus & AHCI_P_IX_SDB) {
+	if ((istatus & AHCI_P_IX_SDB) &&
+	    (ch->pm_present || ch->curr[0].atapi != 0)) {
 		if (ch->caps & AHCI_CAP_SSNTF)
 			sntf = ATA_INL(ch->r_mem, AHCI_P_SNTF);
 		else if (ch->fbs_enabled) {