Re: ISA DMA controller hangs

[Pierre Ossman <drzeus-list@drzeus.cx>]

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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>

If this patch seems ok then I'll make another one for x86_64 (the only
other platform with ISA DMA AFAIK).

I couldn't find who was responsible for the i386 arch so I've cc:ed Linus.

Rgds
Pierre


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Index: linux-wbsd/arch/i386/kernel/i8237.c
===================================================================
--- linux-wbsd/arch/i386/kernel/i8237.c	(revision 0)
+++ linux-wbsd/arch/i386/kernel/i8237.c	(revision 0)
@@ -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 wierd 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);
Index: linux-wbsd/arch/i386/kernel/Makefile
===================================================================
--- linux-wbsd/arch/i386/kernel/Makefile	(revision 153)
+++ linux-wbsd/arch/i386/kernel/Makefile	(working copy)
@@ -7,7 +7,7 @@
 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/