From: Pierre Ossman <drzeus-list@drzeus.cx>

Reset the ISA DMA controller into a known state after a suspend.  Primary
concern was reenabling the cascading DMA channel (4).

Word of warning, I haven't tested this platform since I don't have any
x86_64 hardware. But it shouldn't differ from i386.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 arch/x86_64/kernel/Makefile |    2 -
 arch/x86_64/kernel/i8237.c  |   67 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+), 1 deletion(-)

diff -puN /dev/null arch/x86_64/kernel/i8237.c
--- /dev/null	2003-09-15 06:40:47.000000000 -0700
+++ devel-akpm/arch/x86_64/kernel/i8237.c	2005-07-06 00:31:04.000000000 -0700
@@ -0,0 +1,67 @@
+/*
+ * i8237.c: 8237A DMA controller suspend functions.
+ *
+ * Written by Pierre Ossman, 2005.
+ */
+
+#include <linux/init.h>
+#include <linux/sysdev.h>
+
+#include <asm/dma.h>
+
+/*
+ * This module just handles suspend/resume issues with the
+ * 8237A DMA controller (used for ISA and LPC).
+ * Allocation is handled in kernel/dma.c and normal usage is
+ * in asm/dma.h.
+ */
+
+static int i8237A_resume(struct sys_device *dev)
+{
+	unsigned long flags;
+	int i;
+
+	flags = claim_dma_lock();
+
+	dma_outb(DMA1_RESET_REG, 0);
+	dma_outb(DMA2_RESET_REG, 0);
+
+	for (i = 0;i < 8;i++) {
+		set_dma_addr(i, 0x000000);
+		/* DMA count is a bit weird so this is not 0 */
+		set_dma_count(i, 1);
+	}
+
+	/* Enable cascade DMA or channel 0-3 won't work */
+	enable_dma(4);
+
+	release_dma_lock(flags);
+
+	return 0;
+}
+
+static int i8237A_suspend(struct sys_device *dev, pm_message_t state)
+{
+	return 0;
+}
+
+static struct sysdev_class i8237_sysdev_class = {
+	set_kset_name("i8237"),
+	.suspend = i8237A_suspend,
+	.resume = i8237A_resume,
+};
+
+static struct sys_device device_i8237A = {
+	.id	= 0,
+	.cls	= &i8237_sysdev_class,
+};
+
+static int __init i8237A_init_sysfs(void)
+{
+	int error = sysdev_class_register(&i8237_sysdev_class);
+	if (!error)
+		error = sysdev_register(&device_i8237A);
+	return error;
+}
+
+device_initcall(i8237A_init_sysfs);
diff -puN arch/x86_64/kernel/Makefile~isa-dma-suspend-for-x86_64 arch/x86_64/kernel/Makefile
--- devel/arch/x86_64/kernel/Makefile~isa-dma-suspend-for-x86_64	2005-07-06 00:31:04.000000000 -0700
+++ devel-akpm/arch/x86_64/kernel/Makefile	2005-07-06 00:31:04.000000000 -0700
@@ -7,7 +7,7 @@ EXTRA_AFLAGS	:= -traditional
 obj-y	:= process.o semaphore.o signal.o entry.o traps.o irq.o \
 		ptrace.o time.o ioport.o ldt.o setup.o i8259.o sys_x86_64.o \
 		x8664_ksyms.o i387.o syscall.o vsyscall.o \
-		setup64.o bootflag.o e820.o reboot.o quirks.o
+		setup64.o bootflag.o e820.o reboot.o quirks.o i8237.o
 
 obj-$(CONFIG_X86_MCE)         += mce.o
 obj-$(CONFIG_X86_MCE_INTEL)	+= mce_intel.o
_