[src/trunk]: src/sys/dev/ata add further note about FIS-based switching to at...

[jdolecek <jdolecek%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/f2f6beebb545
branches:  trunk
changeset: 445357:f2f6beebb545
user:      jdolecek <jdolecek%NetBSD.org@localhost>
date:      Wed Oct 24 20:01:13 2018 +0000

description:
add further note about FIS-based switching to atastart()

diffstat:

 sys/dev/ata/ata.c |  12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)

diffs (33 lines):

diff -r 4b1f6f175978 -r f2f6beebb545 sys/dev/ata/ata.c
--- a/sys/dev/ata/ata.c Wed Oct 24 19:46:44 2018 +0000
+++ b/sys/dev/ata/ata.c Wed Oct 24 20:01:13 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ata.c,v 1.143 2018/10/24 19:38:00 jdolecek Exp $       */
+/*     $NetBSD: ata.c,v 1.144 2018/10/24 20:01:13 jdolecek Exp $       */
 
 /*
  * Copyright (c) 1998, 2001 Manuel Bouyer.  All rights reserved.
@@ -25,7 +25,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ata.c,v 1.143 2018/10/24 19:38:00 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ata.c,v 1.144 2018/10/24 20:01:13 jdolecek Exp $");
 
 #include "opt_ata.h"
 
@@ -1053,6 +1053,14 @@
  * are shared.
  *
  * MUST BE CALLED AT splbio()!
+ *
+ * XXX FIS-based switching with PMP
+ * Currently atastart() never schedules concurrent NCQ transfers to more than
+ * one drive, even when channel has several SATA drives attached via PMP.
+ * To support concurrent transfers to different drives with PMP, it would be
+ * necessary to implement FIS-based switching support in controller driver,
+ * and then adjust error handling and recovery to stop assuming at most
+ * one active drive.
  */
 void
 atastart(struct ata_channel *chp)