[ARM] dma: fix dmabounce dma_sync_xxx() implementations

The dmabounce dma_sync_xxx() implementation have been broken for
quite some time; they all copy data between the DMA buffer and
the CPU visible buffer no irrespective of the change of ownership.
(IOW, a DMA_FROM_DEVICE mapping copies data from the DMA buffer
to the CPU buffer during a call to dma_sync_single_for_device().)

Fix it by getting rid of sync_single(), moving the contents into
the recently created dmabounce_sync_for_xxx() functions and adjusting
appropriately.

This also makes it possible to properly support the DMA range sync
functions.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 69 insertions, 101 deletions

diff --git a/arch/arm/common/dmabounce.c b/arch/arm/common/dmabounce.c
index 1cb880b734df..d4b0c608fdee 100644
--- a/arch/arm/common/dmabounce.c
+++ b/arch/arm/common/dmabounce.c
@@ -205,6 +205,21 @@ free_safe_buffer(struct dmabounce_device_info *device_info, struct safe_buffer *
 
 /* ************************************************** */
 
+static struct safe_buffer *find_safe_buffer_dev(struct device *dev,
+                dma_addr_t dma_addr, const char *where)
+{
+        if (!dev || !dev->archdata.dmabounce)
+                return NULL;
+        if (dma_mapping_error(dev, dma_addr)) {
+                if (dev)
+                        dev_err(dev, "Trying to %s invalid mapping\n", where);
+                else
+                        pr_err("unknown device: Trying to %s invalid mapping\n", where);
+                return NULL;
+        }
+        return find_safe_buffer(dev->archdata.dmabounce, dma_addr);
+}
+
 static inline dma_addr_t
 map_single(struct device *dev, void *ptr, size_t size,
                 enum dma_data_direction dir)
@@ -274,19 +289,7 @@ static inline void
 unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
                 enum dma_data_direction dir)
 {
-        struct dmabounce_device_info *device_info = dev->archdata.dmabounce;
-        struct safe_buffer *buf = NULL;
-
-        /*
-         * Trying to unmap an invalid mapping
-         */
-        if (dma_mapping_error(dev, dma_addr)) {
-                dev_err(dev, "Trying to unmap invalid mapping\n");
-                return;
-        }
-
-        if (device_info)
-                buf = find_safe_buffer(device_info, dma_addr);
+        struct safe_buffer *buf = find_safe_buffer_dev(dev, dma_addr, "unmap");
 
         if (buf) {
                 BUG_ON(buf->size != size);
@@ -296,7 +299,7 @@ unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
                         __func__, buf->ptr, virt_to_dma(dev, buf->ptr),
                         buf->safe, buf->safe_dma_addr);
 
-                DO_STATS ( device_info->bounce_count++ );
+                DO_STATS(dev->archdata.dmabounce->bounce_count++);
 
                 if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL) {
                         void *ptr = buf->ptr;
@@ -317,74 +320,7 @@ unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
                         dmac_clean_range(ptr, ptr + size);
                         outer_clean_range(__pa(ptr), __pa(ptr) + size);
                 }
-                free_safe_buffer(device_info, buf);
-        }
-}
-
-static int sync_single(struct device *dev, dma_addr_t dma_addr, size_t size,
-                        enum dma_data_direction dir)
-{
-        struct dmabounce_device_info *device_info = dev->archdata.dmabounce;
-        struct safe_buffer *buf = NULL;
-
-        if (device_info)
-                buf = find_safe_buffer(device_info, dma_addr);
-
-        if (buf) {
-                /*
-                 * Both of these checks from original code need to be
-                 * commented out b/c some drivers rely on the following:
-                 *
-                 * 1) Drivers may map a large chunk of memory into DMA space
-                 *    but only sync a small portion of it. Good example is
-                 *    allocating a large buffer, mapping it, and then
-                 *    breaking it up into small descriptors. No point
-                 *    in syncing the whole buffer if you only have to
-                 *    touch one descriptor.
-                 *
-                 * 2) Buffers that are mapped as DMA_BIDIRECTIONAL are
-                 *    usually only synced in one dir at a time.
-                 *
-                 * See drivers/net/eepro100.c for examples of both cases.
-                 *
-                 * -ds
-                 *
-                 * BUG_ON(buf->size != size);
-                 * BUG_ON(buf->direction != dir);
-                 */
-
-                dev_dbg(dev,
-                        "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)\n",
-                        __func__, buf->ptr, virt_to_dma(dev, buf->ptr),
-                        buf->safe, buf->safe_dma_addr);
-
-                DO_STATS ( device_info->bounce_count++ );
-
-                switch (dir) {
-                case DMA_FROM_DEVICE:
-                        dev_dbg(dev,
-                                "%s: copy back safe %p to unsafe %p size %d\n",
-                                __func__, buf->safe, buf->ptr, size);
-                        memcpy(buf->ptr, buf->safe, size);
-                        break;
-                case DMA_TO_DEVICE:
-                        dev_dbg(dev,
-                                "%s: copy out unsafe %p to safe %p, size %d\n",
-                                __func__,buf->ptr, buf->safe, size);
-                        memcpy(buf->safe, buf->ptr, size);
-                        break;
-                case DMA_BIDIRECTIONAL:
-                        BUG();  /* is this allowed?  what does it mean? */
-                default:
-                        BUG();
-                }
-                /*
-                 * No need to sync the safe buffer - it was allocated
-                 * via the coherent allocators.
-                 */
-                return 0;
-        } else {
-                return 1;
+                free_safe_buffer(dev->archdata.dmabounce, buf);
         }
 }
 
@@ -447,18 +383,54 @@ dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
 int dmabounce_sync_for_cpu(struct device *dev, dma_addr_t addr,
                 unsigned long off, size_t sz, enum dma_data_direction dir)
 {
-        dev_dbg(dev, "%s(dma=%#lx,off=%#lx,sz=%zx,dir=%x)\n",
+        struct safe_buffer *buf;
+
+        dev_dbg(dev, "%s(dma=%#x,off=%#lx,sz=%zx,dir=%x)\n",
                 __func__, addr, off, sz, dir);
-        return sync_single(dev, addr, off + sz, dir);
+
+        buf = find_safe_buffer_dev(dev, addr, __func__);
+        if (!buf)
+                return 1;
+
+        dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)\n",
+                __func__, buf->ptr, virt_to_dma(dev, buf->ptr),
+                buf->safe, buf->safe_dma_addr);
+
+        DO_STATS(dev->archdata.dmabounce->bounce_count++);
+
+        if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL) {
+                dev_dbg(dev, "%s: copy back safe %p to unsafe %p size %d\n",
+                        __func__, buf->safe + off, buf->ptr + off, sz);
+                memcpy(buf->ptr + off, buf->safe + off, sz);
+        }
+        return 0;
 }
 EXPORT_SYMBOL(dmabounce_sync_for_cpu);
 
 int dmabounce_sync_for_device(struct device *dev, dma_addr_t addr,
                 unsigned long off, size_t sz, enum dma_data_direction dir)
 {
-        dev_dbg(dev, "%s(dma=%#lx,off=%#lx,sz=%zx,dir=%x)\n",
+        struct safe_buffer *buf;
+
+        dev_dbg(dev, "%s(dma=%#x,off=%#lx,sz=%zx,dir=%x)\n",
                 __func__, addr, off, sz, dir);
-        return sync_single(dev, addr, off + sz, dir);
+
+        buf = find_safe_buffer_dev(dev, addr, __func__);
+        if (!buf)
+                return 1;
+
+        dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)\n",
+                __func__, buf->ptr, virt_to_dma(dev, buf->ptr),
+                buf->safe, buf->safe_dma_addr);
+
+        DO_STATS(dev->archdata.dmabounce->bounce_count++);
+
+        if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL) {
+                dev_dbg(dev, "%s: copy out unsafe %p to safe %p, size %d\n",
+                        __func__,buf->ptr + off, buf->safe + off, sz);
+                memcpy(buf->safe + off, buf->ptr + off, sz);
+        }
+        return 0;
 }
 EXPORT_SYMBOL(dmabounce_sync_for_device);
 
diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
index c003ad390def..1204dc958c43 100644
--- a/arch/arm/include/asm/dma-mapping.h
+++ b/arch/arm/include/asm/dma-mapping.h
@@ -242,6 +242,15 @@ extern void dmabounce_unregister_dev(struct device *);
 extern int dma_needs_bounce(struct device*, dma_addr_t, size_t);
 
 /*
+ * The DMA API, implemented by dmabounce.c.  See below for descriptions.
+ */
+extern dma_addr_t dma_map_single(struct device *,void *, size_t, enum dma_data_direction);
+extern dma_addr_t dma_map_page(struct device *dev, struct page *page,
+                        unsigned long offset, size_t size,
+                        enum dma_data_direction dir);
+extern void dma_unmap_single(struct device *, dma_addr_t, size_t, enum dma_data_direction);
+
+/*
  * Private functions
  */
 int dmabounce_sync_for_cpu(struct device *, dma_addr_t, unsigned long,
@@ -251,7 +260,6 @@ int dmabounce_sync_for_device(struct device *, dma_addr_t, unsigned long,
 #else
 #define dmabounce_sync_for_cpu(dev,dma,off,sz,dir)      (1)
 #define dmabounce_sync_for_device(dev,dma,off,sz,dir)   (1)
-#endif /* CONFIG_DMABOUNCE */
 
 
 /**
@@ -268,7 +276,6 @@ int dmabounce_sync_for_device(struct device *, dma_addr_t, unsigned long,
  * can regain ownership by calling dma_unmap_single() or
  * dma_sync_single_for_cpu().
  */
-#ifndef CONFIG_DMABOUNCE
 static inline dma_addr_t
 dma_map_single(struct device *dev, void *cpu_addr, size_t size,
                enum dma_data_direction dir)
@@ -278,9 +285,7 @@ dma_map_single(struct device *dev, void *cpu_addr, size_t size,
 
         return virt_to_dma(dev, cpu_addr);
 }
-#else
-extern dma_addr_t dma_map_single(struct device *,void *, size_t, enum dma_data_direction);
-#endif
+
 
 /**
  * dma_map_page - map a portion of a page for streaming DMA
@@ -297,7 +302,6 @@ extern dma_addr_t dma_map_single(struct device *,void *, size_t, enum dma_data_d
  * can regain ownership by calling dma_unmap_page() or
  * dma_sync_single_for_cpu().
  */
-#ifndef CONFIG_DMABOUNCE
 static inline dma_addr_t
 dma_map_page(struct device *dev, struct page *page,
              unsigned long offset, size_t size,
@@ -308,11 +312,6 @@ dma_map_page(struct device *dev, struct page *page,
 
         return page_to_dma(dev, page) + offset;
 }
-#else
-extern dma_addr_t dma_map_page(struct device *dev, struct page *page,
-                        unsigned long offset, size_t size,
-                        enum dma_data_direction dir);
-#endif
 
 /**
  * dma_unmap_single - unmap a single buffer previously mapped
@@ -328,16 +327,13 @@ extern dma_addr_t dma_map_page(struct device *dev, struct page *page,
  * After this call, reads by the CPU to the buffer are guaranteed to see
  * whatever the device wrote there.
  */
-#ifndef CONFIG_DMABOUNCE
 static inline void
 dma_unmap_single(struct device *dev, dma_addr_t handle, size_t size,
                  enum dma_data_direction dir)
 {
         /* nothing to do */
 }
-#else
-extern void dma_unmap_single(struct device *, dma_addr_t, size_t, enum dma_data_direction);
-#endif
+#endif /* CONFIG_DMABOUNCE */
 
 /**
  * dma_unmap_page - unmap a buffer previously mapped through dma_map_page()