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[src/trunk]: src/sys/arch/aarch64/aarch64 Add a note about completion vs orde...
details: https://anonhg.NetBSD.org/src/rev/838b3277a24f
branches: trunk
changeset: 947514:838b3277a24f
user: skrll <skrll%NetBSD.org@localhost>
date: Mon Dec 14 19:32:29 2020 +0000
description:
Add a note about completion vs ordering barrier as well.
diffstat:
sys/arch/aarch64/aarch64/bus_space.c | 8 ++++++--
1 files changed, 6 insertions(+), 2 deletions(-)
diffs (29 lines):
diff -r 2f93007845fc -r 838b3277a24f sys/arch/aarch64/aarch64/bus_space.c
--- a/sys/arch/aarch64/aarch64/bus_space.c Mon Dec 14 19:25:28 2020 +0000
+++ b/sys/arch/aarch64/aarch64/bus_space.c Mon Dec 14 19:32:29 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: bus_space.c,v 1.14 2020/12/14 19:25:28 skrll Exp $ */
+/* $NetBSD: bus_space.c,v 1.15 2020/12/14 19:32:29 skrll Exp $ */
/*
* Copyright (c) 2017 Ryo Shimizu <ryo%nerv.org@localhost>
@@ -27,7 +27,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(1, "$NetBSD: bus_space.c,v 1.14 2020/12/14 19:25:28 skrll Exp $");
+__KERNEL_RCSID(1, "$NetBSD: bus_space.c,v 1.15 2020/12/14 19:32:29 skrll Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@@ -638,6 +638,10 @@
* consulting the page tables), so just issue the barrier
* unconditionally. Chances are either it's necessary or the
* cost is small in comparison to device register I/O.
+ *
+ * The bus_space(9) man page is not clear whether barriers
+ * should enforce ordering or completion. To be safe, use dsb
+ * (ensure completion) here instead of dmb (ordering).
*/
switch (flags) {
case BUS_SPACE_BARRIER_READ:
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