[PATCH] ISA DMA suspend for i386

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

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 68 insertions, 1 deletions

diff --git a/arch/i386/kernel/Makefile b/arch/i386/kernel/Makefile
index 4cc83b322b3..64682a0edac 100644
--- a/arch/i386/kernel/Makefile
+++ b/arch/i386/kernel/Makefile
@@ -7,7 +7,7 @@ extra-y := head.o init_task.o vmlinux.lds
 obj-y	:= process.o semaphore.o signal.o entry.o traps.o irq.o vm86.o \
 		ptrace.o time.o ioport.o ldt.o setup.o i8259.o sys_i386.o \
 		pci-dma.o i386_ksyms.o i387.o dmi_scan.o bootflag.o \
-		doublefault.o quirks.o
+		doublefault.o quirks.o i8237.o
 
 obj-y				+= cpu/
 obj-y				+= timers/
diff --git a/arch/i386/kernel/i8237.c b/arch/i386/kernel/i8237.c
new file mode 100644
index 00000000000..c36d1c006c2
--- /dev/null
+++ b/arch/i386/kernel/i8237.c
@@ -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);