openwrt-xburst/target/linux/ixp4xx/patches-2.6.30/050-disable_dmabounce.patch

--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -374,7 +374,6 @@ config ARCH_IXP4XX
 	select GENERIC_GPIO
 	select GENERIC_TIME
 	select GENERIC_CLOCKEVENTS
-	select DMABOUNCE if PCI
 	help
 	  Support for Intel's IXP4XX (XScale) family of processors.
 
--- a/arch/arm/mach-ixp4xx/Kconfig
+++ b/arch/arm/mach-ixp4xx/Kconfig
@@ -193,6 +193,45 @@ config IXP4XX_INDIRECT_PCI
 	  need to use the indirect method instead. If you don't know
 	  what you need, leave this option unselected.
 
+config IXP4XX_LEGACY_DMABOUNCE
+	bool "legacy PCI DMA bounce support"
+	depends on PCI
+	default n
+	select DMABOUNCE
+	help
+	  The IXP4xx is limited to a 64MB window for PCI DMA, which
+	  requires that PCI accesses above 64MB are bounced via buffers
+	  below 64MB. Furthermore the IXP4xx has an erratum where PCI
+	  read prefetches just below the 64MB limit can trigger lockups.
+
+	  The kernel has traditionally handled these two issue by using
+	  ARM specific DMA bounce support code for all accesses >= 64MB.
+	  That code causes problems of its own, so it is desirable to
+	  disable it. As the kernel now has a workaround for the PCI read
+	  prefetch erratum, it no longer requires the ARM bounce code.
+
+	  Enabling this option makes IXP4xx continue to use the problematic
+	  ARM DMA bounce code. Disabling this option makes IXP4xx use the
+	  kernel's generic bounce code.
+
+	  Say 'N'.
+
+config IXP4XX_ZONE_DMA
+	bool "Support > 64MB RAM"
+	depends on !IXP4XX_LEGACY_DMABOUNCE
+	default y
+	select ZONE_DMA
+	help
+	  The IXP4xx is limited to a 64MB window for PCI DMA, which
+	  requires that PCI accesses above 64MB are bounced via buffers
+	  below 64MB.
+
+	  Disabling this option allows you to omit the support code for
+	  DMA-able memory allocations and DMA bouncing, but the kernel
+	  will then not work properly if more than 64MB of RAM is present.
+
+	  Say 'Y' unless your platform is limited to <= 64MB of RAM.
+
 config IXP4XX_QMGR
 	tristate "IXP4xx Queue Manager support"
 	help
--- a/arch/arm/mach-ixp4xx/common-pci.c
+++ b/arch/arm/mach-ixp4xx/common-pci.c
@@ -321,27 +321,38 @@ static int abort_handler(unsigned long a
  */
 static int ixp4xx_pci_platform_notify(struct device *dev)
 {
-	if(dev->bus == &pci_bus_type) {
-		*dev->dma_mask =  SZ_64M - 1;
+	if (dev->bus == &pci_bus_type) {
+		*dev->dma_mask = SZ_64M - 1;
 		dev->coherent_dma_mask = SZ_64M - 1;
+#ifdef CONFIG_DMABOUNCE
 		dmabounce_register_dev(dev, 2048, 4096);
+#endif
 	}
 	return 0;
 }
 
 static int ixp4xx_pci_platform_notify_remove(struct device *dev)
 {
-	if(dev->bus == &pci_bus_type) {
+#ifdef CONFIG_DMABOUNCE
+	if (dev->bus == &pci_bus_type)
 		dmabounce_unregister_dev(dev);
-	}
+#endif
 	return 0;
 }
 
+#ifdef CONFIG_DMABOUNCE
 int dma_needs_bounce(struct device *dev, dma_addr_t dma_addr, size_t size)
 {
+	/* Note that this returns true for the last page below 64M due to
+	 * IXP4xx erratum 15 (SCR 1289), which states that PCI prefetches
+	 * can cross the boundary between valid memory and a reserved region
+	 * causing AHB bus errors and a lock-up.
+	 */
 	return (dev->bus == &pci_bus_type ) && ((dma_addr + size) >= SZ_64M);
 }
+#endif
 
+#ifdef CONFIG_ZONE_DMA
 /*
  * Only first 64MB of memory can be accessed via PCI.
  * We use GFP_DMA to allocate safe buffers to do map/unmap.
@@ -364,6 +375,7 @@ void __init ixp4xx_adjust_zones(int node
 	zhole_size[1] = zhole_size[0];
 	zhole_size[0] = 0;
 }
+#endif
 
 void __init ixp4xx_pci_preinit(void)
 {
@@ -517,19 +529,35 @@ struct pci_bus * __devinit ixp4xx_scan_b
 int
 pci_set_dma_mask(struct pci_dev *dev, u64 mask)
 {
-	if (mask >= SZ_64M - 1 )
+#ifdef CONFIG_DMABOUNCE
+	if (mask >= SZ_64M - 1)
 		return 0;
 
 	return -EIO;
+#else
+	/* Only honour masks < SZ_64M. Silently ignore masks >= SZ_64M
+	   as generic drivers do not know about IXP4xx PCI DMA quirks. */
+	if (mask < SZ_64M)
+		dev->dma_mask = mask;
+	return 0;
+#endif
 }
     
 int
 pci_set_consistent_dma_mask(struct pci_dev *dev, u64 mask)
 {
-	if (mask >= SZ_64M - 1 )
+#ifdef CONFIG_DMABOUNCE
+	if (mask >= SZ_64M - 1)
 		return 0;
 
 	return -EIO;
+#else
+	/* Only honour masks < SZ_64M. Silently ignore masks >= SZ_64M
+	   as generic drivers do not know about IXP4xx PCI DMA quirks. */
+	if (mask < SZ_64M)
+		dev->dev.coherent_dma_mask = mask;
+	return 0;
+#endif
 }
 
 EXPORT_SYMBOL(ixp4xx_pci_read);
--- a/arch/arm/mach-ixp4xx/include/mach/memory.h
+++ b/arch/arm/mach-ixp4xx/include/mach/memory.h
@@ -16,10 +16,12 @@
 
 #if !defined(__ASSEMBLY__) && defined(CONFIG_PCI)
 
+#ifdef CONFIG_ZONE_DMA
 void ixp4xx_adjust_zones(int node, unsigned long *size, unsigned long *holes);
 
 #define arch_adjust_zones(node, size, holes) \
 	ixp4xx_adjust_zones(node, size, holes)
+#endif
 
 #define ISA_DMA_THRESHOLD (SZ_64M - 1)
 #define MAX_DMA_ADDRESS		(PAGE_OFFSET + SZ_64M)