i386: Optional ZONE_DMA

ZONE_DMA depends on GENERIC_ISA_DMA. We allow the user to configure
GENERIC_ISA_DMA. If it is switched off then we buid a kernel without
ZONE_DMA.

Note that this patch is incomplete: All device drivers that use GENERIC_ISA_DMA
need to depend on it. This was not tested for i386 NUMA and other miscalleneous
configuration. But it works on my desktop (dual core Pentium).

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.18-rc1-mm1/arch/i386/kernel/setup.c
===================================================================
--- linux-2.6.18-rc1-mm1.orig/arch/i386/kernel/setup.c	2006-07-10 10:33:41.638305144 -0700
+++ linux-2.6.18-rc1-mm1/arch/i386/kernel/setup.c	2006-07-10 11:13:53.043755570 -0700
@@ -1208,15 +1208,19 @@ void __init zone_sizes_init(void)
 	max_dma = virt_to_phys((char *)MAX_DMA_ADDRESS) >> PAGE_SHIFT;
 	low = max_low_pfn;
 
+#ifdef CONFIG_ZONE_DMA
 	if (low < max_dma)
 		zones_size[ZONE_DMA] = low;
 	else {
 		zones_size[ZONE_DMA] = max_dma;
 		zones_size[ZONE_NORMAL] = low - max_dma;
+	}
+#else
+	zones_size[ZONE_NORMAL] = low;
+#endif
 #ifdef CONFIG_HIGHMEM
-		zones_size[ZONE_HIGHMEM] = highend_pfn - low;
+	zones_size[ZONE_HIGHMEM] = highend_pfn - low;
 #endif
-	}
 	free_area_init(zones_size);
 }
 #else
Index: linux-2.6.18-rc1-mm1/arch/i386/Kconfig
===================================================================
--- linux-2.6.18-rc1-mm1.orig/arch/i386/Kconfig	2006-07-10 10:33:41.617798603 -0700
+++ linux-2.6.18-rc1-mm1/arch/i386/Kconfig	2006-07-10 11:13:53.065238617 -0700
@@ -41,10 +41,6 @@ config MMU
 config SBUS
 	bool
 
-config GENERIC_ISA_DMA
-	bool
-	default y
-
 config GENERIC_IOMAP
 	bool
 	default y
@@ -344,6 +340,15 @@ config VM86
           XFree86 to initialize some video cards via BIOS. Disabling this
           option saves about 6k.
 
+config GENERIC_ISA_DMA
+	bool "ISA DMA zone (to support ISA legacy DMA)"
+	default y
+	help
+	  If DMA for ISA boards needs to be supported then this option
+	  needs to be enabled. An additional DMA zone for <16MB memory
+	  will be created and memory below 16MB will be used for those
+	  devices.
+
 config TOSHIBA
 	tristate "Toshiba Laptop support"
 	---help---
Index: linux-2.6.18-rc1-mm1/arch/i386/kernel/Makefile
===================================================================
--- linux-2.6.18-rc1-mm1.orig/arch/i386/kernel/Makefile	2006-07-05 21:09:49.000000000 -0700
+++ linux-2.6.18-rc1-mm1/arch/i386/kernel/Makefile	2006-07-10 11:13:53.076956643 -0700
@@ -7,8 +7,9 @@ extra-y := head.o init_task.o vmlinux.ld
 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_i386.o \
 		pci-dma.o i386_ksyms.o i387.o bootflag.o \
-		quirks.o i8237.o topology.o alternative.o i8253.o tsc.o
+		quirks.o topology.o alternative.o i8253.o tsc.o
 
+obj-$(CONFIG_GENERIC_ISA_DMA)	+= i8237.o
 obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
 obj-y				+= cpu/
 obj-y				+= acpi/