[src/trunk]: src/sys/arch/arm/arm32 No need to allocate bounce buffers if we ...

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

details:   https://anonhg.NetBSD.org/src/rev/557f608bbeec
branches:  trunk
changeset: 957997:557f608bbeec
user:      jmcneill <jmcneill%NetBSD.org@localhost>
date:      Sat Dec 19 23:22:18 2020 +0000

description:
No need to allocate bounce buffers if we have a single range that covers
all of physical memory.

diffstat:

 sys/arch/arm/arm32/bus_dma.c |  23 +++++++++++++++++++----
 1 files changed, 19 insertions(+), 4 deletions(-)

diffs (44 lines):

diff -r cb5d79de42c7 -r 557f608bbeec sys/arch/arm/arm32/bus_dma.c
--- a/sys/arch/arm/arm32/bus_dma.c      Sat Dec 19 22:33:11 2020 +0000
+++ b/sys/arch/arm/arm32/bus_dma.c      Sat Dec 19 23:22:18 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: bus_dma.c,v 1.126 2020/12/04 07:12:57 skrll Exp $      */
+/*     $NetBSD: bus_dma.c,v 1.127 2020/12/19 23:22:18 jmcneill Exp $   */
 
 /*-
  * Copyright (c) 1996, 1997, 1998, 2020 The NetBSD Foundation, Inc.
@@ -36,7 +36,7 @@
 #include "opt_cputypes.h"
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: bus_dma.c,v 1.126 2020/12/04 07:12:57 skrll Exp $");
+__KERNEL_RCSID(0, "$NetBSD: bus_dma.c,v 1.127 2020/12/19 23:22:18 jmcneill Exp $");
 
 #include <sys/param.h>
 
@@ -368,8 +368,23 @@
                        goto out;
        }
 
-       if (t->_ranges != NULL)
-               cookieflags |= _BUS_DMA_MIGHT_NEED_BOUNCE;
+       if (t->_ranges != NULL) {
+               /*
+                * If ranges are defined, we may have to bounce. The only
+                * exception is if there is exactly one range that covers
+                * all of physical memory.
+                */
+               switch (t->_nranges) {
+               case 1:
+                       if (t->_ranges[0].dr_sysbase == 0 &&
+                           t->_ranges[0].dr_len == UINTPTR_MAX) {
+                               break;
+                       }
+                       /* FALLTHROUGH */
+               default:
+                       cookieflags |= _BUS_DMA_MIGHT_NEED_BOUNCE;
+               }
+       }
 
        if ((cookieflags & _BUS_DMA_MIGHT_NEED_BOUNCE) == 0) {
                STAT_INCR(creates);