MIPS: HIGHMEM DMA on noncoherent MIPS32 processors

[v4: Patch applies to linux-queue.git with kmap_atomic patches:
 https://patchwork.kernel.org/patch/189932/
 https://patchwork.kernel.org/patch/194552/
 https://patchwork.kernel.org/patch/189912/ ]

The MIPS DMA coherency functions do not work properly (i.e. kernel oops)
when HIGHMEM pages are passed in as arguments.  Use kmap_atomic() to
temporarily map high pages for cache maintenance operations.

Tested on a 2.6.36-rc7 1GB HIGHMEM SMP no-alias system.

Signed-off-by: Dezhong Diao <dediao@cisco.com>
Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Cc: Dezhong Diao <dediao@cisco.com>
Cc: David Daney <ddaney@caviumnetworks.com>
Cc: David VomLehn <dvomlehn@cisco.com>
Cc: Sergei Shtylyov <sshtylyov@mvista.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/1695/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 68 insertions, 46 deletions

diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c
index 21ea14efb837..46084912e588 100644
--- a/arch/mips/mm/dma-default.c
+++ b/arch/mips/mm/dma-default.c
@@ -15,18 +15,18 @@
 #include <linux/scatterlist.h>
 #include <linux/string.h>
 #include <linux/gfp.h>
+#include <linux/highmem.h>
 
 #include <asm/cache.h>
 #include <asm/io.h>
 
 #include <dma-coherence.h>
 
-static inline unsigned long dma_addr_to_virt(struct device *dev,
+static inline struct page *dma_addr_to_page(struct device *dev,
         dma_addr_t dma_addr)
 {
-        unsigned long addr = plat_dma_addr_to_phys(dev, dma_addr);
-
-        return (unsigned long)phys_to_virt(addr);
+        return pfn_to_page(
+                plat_dma_addr_to_phys(dev, dma_addr) >> PAGE_SHIFT);
 }
 
 /*
@@ -148,20 +148,20 @@ static void mips_dma_free_coherent(struct device *dev, size_t size, void *vaddr,
         free_pages(addr, get_order(size));
 }
 
-static inline void __dma_sync(unsigned long addr, size_t size,
+static inline void __dma_sync_virtual(void *addr, size_t size,
         enum dma_data_direction direction)
 {
         switch (direction) {
         case DMA_TO_DEVICE:
-                dma_cache_wback(addr, size);
+                dma_cache_wback((unsigned long)addr, size);
                 break;
 
         case DMA_FROM_DEVICE:
-                dma_cache_inv(addr, size);
+                dma_cache_inv((unsigned long)addr, size);
                 break;
 
         case DMA_BIDIRECTIONAL:
-                dma_cache_wback_inv(addr, size);
+                dma_cache_wback_inv((unsigned long)addr, size);
                 break;
 
         default:
@@ -169,12 +169,49 @@ static inline void __dma_sync(unsigned long addr, size_t size,
         }
 }
 
+/*
+ * A single sg entry may refer to multiple physically contiguous
+ * pages. But we still need to process highmem pages individually.
+ * If highmem is not configured then the bulk of this loop gets
+ * optimized out.
+ */
+static inline void __dma_sync(struct page *page,
+        unsigned long offset, size_t size, enum dma_data_direction direction)
+{
+        size_t left = size;
+
+        do {
+                size_t len = left;
+
+                if (PageHighMem(page)) {
+                        void *addr;
+
+                        if (offset + len > PAGE_SIZE) {
+                                if (offset >= PAGE_SIZE) {
+                                        page += offset >> PAGE_SHIFT;
+                                        offset &= ~PAGE_MASK;
+                                }
+                                len = PAGE_SIZE - offset;
+                        }
+
+                        addr = kmap_atomic(page);
+                        __dma_sync_virtual(addr + offset, len, direction);
+                        kunmap_atomic(addr);
+                } else
+                        __dma_sync_virtual(page_address(page) + offset,
+                                           size, direction);
+                offset = 0;
+                page++;
+                left -= len;
+        } while (left);
+}
+
 static void mips_dma_unmap_page(struct device *dev, dma_addr_t dma_addr,
         size_t size, enum dma_data_direction direction, struct dma_attrs *attrs)
 {
         if (cpu_is_noncoherent_r10000(dev))
-                __dma_sync(dma_addr_to_virt(dev, dma_addr), size,
-                           direction);
+                __dma_sync(dma_addr_to_page(dev, dma_addr),
+                           dma_addr & ~PAGE_MASK, size, direction);
 
         plat_unmap_dma_mem(dev, dma_addr, size, direction);
 }
@@ -185,13 +222,11 @@ static int mips_dma_map_sg(struct device *dev, struct scatterlist *sg,
         int i;
 
         for (i = 0; i < nents; i++, sg++) {
-                unsigned long addr;
-
-                addr = (unsigned long) sg_virt(sg);
-                if (!plat_device_is_coherent(dev) && addr)
-                        __dma_sync(addr, sg->length, direction);
-                sg->dma_address = plat_map_dma_mem(dev,
-                                                   (void *)addr, sg->length);
+                if (!plat_device_is_coherent(dev))
+                        __dma_sync(sg_page(sg), sg->offset, sg->length,
+                                   direction);
+                sg->dma_address = plat_map_dma_mem_page(dev, sg_page(sg)) +
+                                  sg->offset;
         }
 
         return nents;
@@ -201,30 +236,23 @@ static dma_addr_t mips_dma_map_page(struct device *dev, struct page *page,
         unsigned long offset, size_t size, enum dma_data_direction direction,
         struct dma_attrs *attrs)
 {
-        unsigned long addr;
-
-        addr = (unsigned long) page_address(page) + offset;
-
         if (!plat_device_is_coherent(dev))
-                __dma_sync(addr, size, direction);
+                __dma_sync(page, offset, size, direction);
 
-        return plat_map_dma_mem(dev, (void *)addr, size);
+        return plat_map_dma_mem_page(dev, page) + offset;
 }
 
 static void mips_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
         int nhwentries, enum dma_data_direction direction,
         struct dma_attrs *attrs)
 {
-        unsigned long addr;
         int i;
 
         for (i = 0; i < nhwentries; i++, sg++) {
                 if (!plat_device_is_coherent(dev) &&
-                    direction != DMA_TO_DEVICE) {
-                        addr = (unsigned long) sg_virt(sg);
-                        if (addr)
-                                __dma_sync(addr, sg->length, direction);
-                }
+                    direction != DMA_TO_DEVICE)
+                        __dma_sync(sg_page(sg), sg->offset, sg->length,
+                                   direction);
                 plat_unmap_dma_mem(dev, sg->dma_address, sg->length, direction);
         }
 }
@@ -232,24 +260,18 @@ static void mips_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
 static void mips_dma_sync_single_for_cpu(struct device *dev,
         dma_addr_t dma_handle, size_t size, enum dma_data_direction direction)
 {
-        if (cpu_is_noncoherent_r10000(dev)) {
-                unsigned long addr;
-
-                addr = dma_addr_to_virt(dev, dma_handle);
-                __dma_sync(addr, size, direction);
-        }
+        if (cpu_is_noncoherent_r10000(dev))
+                __dma_sync(dma_addr_to_page(dev, dma_handle),
+                           dma_handle & ~PAGE_MASK, size, direction);
 }
 
 static void mips_dma_sync_single_for_device(struct device *dev,
         dma_addr_t dma_handle, size_t size, enum dma_data_direction direction)
 {
         plat_extra_sync_for_device(dev);
-        if (!plat_device_is_coherent(dev)) {
-                unsigned long addr;
-
-                addr = dma_addr_to_virt(dev, dma_handle);
-                __dma_sync(addr, size, direction);
-        }
+        if (!plat_device_is_coherent(dev))
+                __dma_sync(dma_addr_to_page(dev, dma_handle),
+                           dma_handle & ~PAGE_MASK, size, direction);
 }
 
 static void mips_dma_sync_sg_for_cpu(struct device *dev,
@@ -260,8 +282,8 @@ static void mips_dma_sync_sg_for_cpu(struct device *dev,
         /* Make sure that gcc doesn't leave the empty loop body.  */
         for (i = 0; i < nelems; i++, sg++) {
                 if (cpu_is_noncoherent_r10000(dev))
-                        __dma_sync((unsigned long)page_address(sg_page(sg)),
-                                   sg->length, direction);
+                        __dma_sync(sg_page(sg), sg->offset, sg->length,
+                                   direction);
         }
 }
 
@@ -273,8 +295,8 @@ static void mips_dma_sync_sg_for_device(struct device *dev,
         /* Make sure that gcc doesn't leave the empty loop body.  */
         for (i = 0; i < nelems; i++, sg++) {
                 if (!plat_device_is_coherent(dev))
-                        __dma_sync((unsigned long)page_address(sg_page(sg)),
-                                   sg->length, direction);
+                        __dma_sync(sg_page(sg), sg->offset, sg->length,
+                                   direction);
         }
 }
 
@@ -295,7 +317,7 @@ void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
 
         plat_extra_sync_for_device(dev);
         if (!plat_device_is_coherent(dev))
-                __dma_sync((unsigned long)vaddr, size, direction);
+                __dma_sync_virtual(vaddr, size, direction);
 }
 
 EXPORT_SYMBOL(dma_cache_sync);