powerpc: Add support for swiotlb on 32-bit

This patch includes the basic infrastructure to use swiotlb
bounce buffering on 32-bit powerpc.  It is not yet enabled on
any platforms.  Probably the most interesting bit is the
addition of addr_needs_map to dma_ops - we need this as
a dma_op because the decision of whether or not an addr
can be mapped by a device is device-specific.

Signed-off-by: Becky Bruce <beckyb@kernel.crashing.org>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

8 files changed, 226 insertions, 2 deletions

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index ff755398ce28..93a61898b259 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -300,9 +300,19 @@ config IOMMU_VMERGE
 config IOMMU_HELPER
         def_bool PPC64
 
+config SWIOTLB
+        bool "SWIOTLB support"
+        default n
+        select IOMMU_HELPER
+        ---help---
+          Support for IO bounce buffering for systems without an IOMMU.
+          This allows us to DMA to the full physical address space on
+          platforms where the size of a physical address is larger
+          than the bus address.  Not all platforms support this.
+
 config PPC_NEED_DMA_SYNC_OPS
         def_bool y
-        depends on NOT_COHERENT_CACHE
+        depends on (NOT_COHERENT_CACHE || SWIOTLB)
 
 config HOTPLUG_CPU
         bool "Support for enabling/disabling CPUs"
diff --git a/arch/powerpc/include/asm/dma-mapping.h b/arch/powerpc/include/asm/dma-mapping.h
index cb448d68452c..3d9e887c3c0c 100644
--- a/arch/powerpc/include/asm/dma-mapping.h
+++ b/arch/powerpc/include/asm/dma-mapping.h
@@ -15,9 +15,18 @@
 #include <linux/scatterlist.h>
 #include <linux/dma-attrs.h>
 #include <asm/io.h>
+#include <asm/swiotlb.h>
 
 #define DMA_ERROR_CODE          (~(dma_addr_t)0x0)
 
+/* Some dma direct funcs must be visible for use in other dma_ops */
+extern void *dma_direct_alloc_coherent(struct device *dev, size_t size,
+                                       dma_addr_t *dma_handle, gfp_t flag);
+extern void dma_direct_free_coherent(struct device *dev, size_t size,
+                                     void *vaddr, dma_addr_t dma_handle);
+
+extern unsigned long get_dma_direct_offset(struct device *dev);
+
 #ifdef CONFIG_NOT_COHERENT_CACHE
 /*
  * DMA-consistent mapping functions for PowerPCs that don't support
@@ -78,6 +87,8 @@ struct dma_mapping_ops {
                                 dma_addr_t dma_address, size_t size,
                                 enum dma_data_direction direction,
                                 struct dma_attrs *attrs);
+        int             (*addr_needs_map)(struct device *dev, dma_addr_t addr,
+                                size_t size);
 #ifdef CONFIG_PPC_NEED_DMA_SYNC_OPS
         void            (*sync_single_range_for_cpu)(struct device *hwdev,
                                 dma_addr_t dma_handle, unsigned long offset,
diff --git a/arch/powerpc/include/asm/swiotlb.h b/arch/powerpc/include/asm/swiotlb.h
new file mode 100644
index 000000000000..30891d6e2bc1
--- /dev/null
+++ b/arch/powerpc/include/asm/swiotlb.h
@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2009 Becky Bruce, Freescale Semiconductor
+ *
+ * This program is free software; you can redistribute  it and/or modify it
+ * under  the terms of  the GNU General  Public License as published by the
+ * Free Software Foundation;  either version 2 of the  License, or (at your
+ * option) any later version.
+ *
+ */
+
+#ifndef __ASM_SWIOTLB_H
+#define __ASM_SWIOTLB_H
+
+#include <linux/swiotlb.h>
+
+extern struct dma_mapping_ops swiotlb_dma_ops;
+extern struct dma_mapping_ops swiotlb_pci_dma_ops;
+
+int swiotlb_arch_address_needs_mapping(struct device *, dma_addr_t,
+                                       size_t size);
+
+static inline void dma_mark_clean(void *addr, size_t size) {}
+
+extern unsigned int ppc_swiotlb_enable;
+int __init swiotlb_setup_bus_notifier(void);
+
+#endif /* __ASM_SWIOTLB_H */
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index cbc359f69e00..65cf36502aa6 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -82,6 +82,7 @@ obj-$(CONFIG_SMP)		+= smp.o
 obj-$(CONFIG_KPROBES)           += kprobes.o
 obj-$(CONFIG_PPC_UDBG_16550)    += legacy_serial.o udbg_16550.o
 obj-$(CONFIG_STACKTRACE)        += stacktrace.o
+obj-$(CONFIG_SWIOTLB)           += dma-swiotlb.o
 
 pci64-$(CONFIG_PPC64)           += pci_dn.o isa-bridge.o
 obj-$(CONFIG_PCI)               += pci_$(CONFIG_WORD_SIZE).o $(pci64-y) \
diff --git a/arch/powerpc/kernel/dma-swiotlb.c b/arch/powerpc/kernel/dma-swiotlb.c
new file mode 100644
index 000000000000..68ccf11e4f19
--- /dev/null
+++ b/arch/powerpc/kernel/dma-swiotlb.c
@@ -0,0 +1,163 @@
+/*
+ * Contains routines needed to support swiotlb for ppc.
+ *
+ * Copyright (C) 2009 Becky Bruce, Freescale Semiconductor
+ *
+ * This program is free software; you can redistribute  it and/or modify it
+ * under  the terms of  the GNU General  Public License as published by the
+ * Free Software Foundation;  either version 2 of the  License, or (at your
+ * option) any later version.
+ *
+ */
+
+#include <linux/dma-mapping.h>
+#include <linux/pfn.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/pci.h>
+
+#include <asm/machdep.h>
+#include <asm/swiotlb.h>
+#include <asm/dma.h>
+#include <asm/abs_addr.h>
+
+int swiotlb __read_mostly;
+unsigned int ppc_swiotlb_enable;
+
+void *swiotlb_bus_to_virt(struct device *hwdev, dma_addr_t addr)
+{
+        unsigned long pfn = PFN_DOWN(swiotlb_bus_to_phys(hwdev, addr));
+        void *pageaddr = page_address(pfn_to_page(pfn));
+
+        if (pageaddr != NULL)
+                return pageaddr + (addr % PAGE_SIZE);
+        return NULL;
+}
+
+dma_addr_t swiotlb_phys_to_bus(struct device *hwdev, phys_addr_t paddr)
+{
+        return paddr + get_dma_direct_offset(hwdev);
+}
+
+phys_addr_t swiotlb_bus_to_phys(struct device *hwdev, dma_addr_t baddr)
+
+{
+        return baddr - get_dma_direct_offset(hwdev);
+}
+
+/*
+ * Determine if an address needs bounce buffering via swiotlb.
+ * Going forward I expect the swiotlb code to generalize on using
+ * a dma_ops->addr_needs_map, and this function will move from here to the
+ * generic swiotlb code.
+ */
+int
+swiotlb_arch_address_needs_mapping(struct device *hwdev, dma_addr_t addr,
+                                   size_t size)
+{
+        struct dma_mapping_ops *dma_ops = get_dma_ops(hwdev);
+
+        BUG_ON(!dma_ops);
+        return dma_ops->addr_needs_map(hwdev, addr, size);
+}
+
+/*
+ * Determine if an address is reachable by a pci device, or if we must bounce.
+ */
+static int
+swiotlb_pci_addr_needs_map(struct device *hwdev, dma_addr_t addr, size_t size)
+{
+        u64 mask = dma_get_mask(hwdev);
+        dma_addr_t max;
+        struct pci_controller *hose;
+        struct pci_dev *pdev = to_pci_dev(hwdev);
+
+        hose = pci_bus_to_host(pdev->bus);
+        max = hose->dma_window_base_cur + hose->dma_window_size;
+
+        /* check that we're within mapped pci window space */
+        if ((addr + size > max) | (addr < hose->dma_window_base_cur))
+                return 1;
+
+        return !is_buffer_dma_capable(mask, addr, size);
+}
+
+static int
+swiotlb_addr_needs_map(struct device *hwdev, dma_addr_t addr, size_t size)
+{
+        return !is_buffer_dma_capable(dma_get_mask(hwdev), addr, size);
+}
+
+
+/*
+ * At the moment, all platforms that use this code only require
+ * swiotlb to be used if we're operating on HIGHMEM.  Since
+ * we don't ever call anything other than map_sg, unmap_sg,
+ * map_page, and unmap_page on highmem, use normal dma_ops
+ * for everything else.
+ */
+struct dma_mapping_ops swiotlb_dma_ops = {
+        .alloc_coherent = dma_direct_alloc_coherent,
+        .free_coherent = dma_direct_free_coherent,
+        .map_sg = swiotlb_map_sg_attrs,
+        .unmap_sg = swiotlb_unmap_sg_attrs,
+        .dma_supported = swiotlb_dma_supported,
+        .map_page = swiotlb_map_page,
+        .unmap_page = swiotlb_unmap_page,
+        .addr_needs_map = swiotlb_addr_needs_map,
+        .sync_single_range_for_cpu = swiotlb_sync_single_range_for_cpu,
+        .sync_single_range_for_device = swiotlb_sync_single_range_for_device,
+        .sync_sg_for_cpu = swiotlb_sync_sg_for_cpu,
+        .sync_sg_for_device = swiotlb_sync_sg_for_device
+};
+
+struct dma_mapping_ops swiotlb_pci_dma_ops = {
+        .alloc_coherent = dma_direct_alloc_coherent,
+        .free_coherent = dma_direct_free_coherent,
+        .map_sg = swiotlb_map_sg_attrs,
+        .unmap_sg = swiotlb_unmap_sg_attrs,
+        .dma_supported = swiotlb_dma_supported,
+        .map_page = swiotlb_map_page,
+        .unmap_page = swiotlb_unmap_page,
+        .addr_needs_map = swiotlb_pci_addr_needs_map,
+        .sync_single_range_for_cpu = swiotlb_sync_single_range_for_cpu,
+        .sync_single_range_for_device = swiotlb_sync_single_range_for_device,
+        .sync_sg_for_cpu = swiotlb_sync_sg_for_cpu,
+        .sync_sg_for_device = swiotlb_sync_sg_for_device
+};
+
+static int ppc_swiotlb_bus_notify(struct notifier_block *nb,
+                                  unsigned long action, void *data)
+{
+        struct device *dev = data;
+
+        /* We are only intereted in device addition */
+        if (action != BUS_NOTIFY_ADD_DEVICE)
+                return 0;
+
+        /* May need to bounce if the device can't address all of DRAM */
+        if (dma_get_mask(dev) < lmb_end_of_DRAM())
+                set_dma_ops(dev, &swiotlb_dma_ops);
+
+        return NOTIFY_DONE;
+}
+
+static struct notifier_block ppc_swiotlb_plat_bus_notifier = {
+        .notifier_call = ppc_swiotlb_bus_notify,
+        .priority = 0,
+};
+
+static struct notifier_block ppc_swiotlb_of_bus_notifier = {
+        .notifier_call = ppc_swiotlb_bus_notify,
+        .priority = 0,
+};
+
+int __init swiotlb_setup_bus_notifier(void)
+{
+        bus_register_notifier(&platform_bus_type,
+                              &ppc_swiotlb_plat_bus_notifier);
+        bus_register_notifier(&of_platform_bus_type,
+                              &ppc_swiotlb_of_bus_notifier);
+
+        return 0;
+}
diff --git a/arch/powerpc/kernel/dma.c b/arch/powerpc/kernel/dma.c
index 6b02793dc75b..20a60d661ba8 100644
--- a/arch/powerpc/kernel/dma.c
+++ b/arch/powerpc/kernel/dma.c
@@ -19,7 +19,7 @@
  * default the offset is PCI_DRAM_OFFSET.
  */
 
-static unsigned long get_dma_direct_offset(struct device *dev)
+unsigned long get_dma_direct_offset(struct device *dev)
 {
         if (dev)
                 return (unsigned long)dev->archdata.dma_data;
diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
index 9e1ca745d8f0..1d154248cf40 100644
--- a/arch/powerpc/kernel/setup_32.c
+++ b/arch/powerpc/kernel/setup_32.c
@@ -39,6 +39,7 @@
 #include <asm/serial.h>
 #include <asm/udbg.h>
 #include <asm/mmu_context.h>
+#include <asm/swiotlb.h>
 
 #include "setup.h"
 
@@ -332,6 +333,11 @@ void __init setup_arch(char **cmdline_p)
                 ppc_md.setup_arch();
         if ( ppc_md.progress ) ppc_md.progress("arch: exit", 0x3eab);
 
+#ifdef CONFIG_SWIOTLB
+        if (ppc_swiotlb_enable)
+                swiotlb_init();
+#endif
+
         paging_init();
 
         /* Initialize the MMU context management stuff */
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 42221055f0c4..f46548e66045 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -61,6 +61,7 @@
 #include <asm/xmon.h>
 #include <asm/udbg.h>
 #include <asm/kexec.h>
+#include <asm/swiotlb.h>
 
 #include "setup.h"
 
@@ -527,6 +528,11 @@ void __init setup_arch(char **cmdline_p)
         if (ppc_md.setup_arch)
                 ppc_md.setup_arch();
 
+#ifdef CONFIG_SWIOTLB
+        if (ppc_swiotlb_enable)
+                swiotlb_init();
+#endif
+
         paging_init();
         ppc64_boot_msg(0x15, "Setup Done");
 }