[ARM] 3537/1: Rework DMA-bounce locking for finer granularity

Patch from Kevin Hilman

This time with IRQ versions of locks.

Rework also enables compatability with realtime-preemption patch.
With the current locking via interrupt disabling, under RT,
potentially sleeping functions can be called with interrupts
disabled.

Signed-off-by: Kevin Hilman <khilman@mvista.com>
Signed-off-by: Deepak Saxena <dsaxena@plexity.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 21 insertions, 46 deletions

diff --git a/arch/arm/common/dmabounce.c b/arch/arm/common/dmabounce.c
index 7971d0dc6892..5b7c26395b44 100644
--- a/arch/arm/common/dmabounce.c
+++ b/arch/arm/common/dmabounce.c
@@ -77,6 +77,8 @@ struct dmabounce_device_info {
 #endif
         struct dmabounce_pool   small;
         struct dmabounce_pool   large;
+
+        rwlock_t lock;
 };
 
 static LIST_HEAD(dmabounce_devs);
@@ -116,6 +118,7 @@ alloc_safe_buffer(struct dmabounce_device_info *device_info, void *ptr,
         struct safe_buffer *buf;
         struct dmabounce_pool *pool;
         struct device *dev = device_info->dev;
+        unsigned long flags;
 
         dev_dbg(dev, "%s(ptr=%p, size=%d, dir=%d)\n",
                 __func__, ptr, size, dir);
@@ -163,8 +166,12 @@ alloc_safe_buffer(struct dmabounce_device_info *device_info, void *ptr,
                 print_alloc_stats(device_info);
 #endif
 
+        write_lock_irqsave(&device_info->lock, flags);
+
         list_add(&buf->node, &device_info->safe_buffers);
 
+        write_unlock_irqrestore(&device_info->lock, flags);
+
         return buf;
 }
 
@@ -172,22 +179,32 @@ alloc_safe_buffer(struct dmabounce_device_info *device_info, void *ptr,
 static inline struct safe_buffer *
 find_safe_buffer(struct dmabounce_device_info *device_info, dma_addr_t safe_dma_addr)
 {
-        struct safe_buffer *b;
+        struct safe_buffer *b = NULL;
+        unsigned long flags;
+
+        read_lock_irqsave(&device_info->lock, flags);
 
         list_for_each_entry(b, &device_info->safe_buffers, node)
                 if (b->safe_dma_addr == safe_dma_addr)
-                        return b;
+                        break;
 
-        return NULL;
+        read_unlock_irqrestore(&device_info->lock, flags);
+        return b;
 }
 
 static inline void
 free_safe_buffer(struct dmabounce_device_info *device_info, struct safe_buffer *buf)
 {
+        unsigned long flags;
+
         dev_dbg(device_info->dev, "%s(buf=%p)\n", __func__, buf);
 
+        write_lock_irqsave(&device_info->lock, flags);
+
         list_del(&buf->node);
 
+        write_unlock_irqrestore(&device_info->lock, flags);
+
         if (buf->pool)
                 dma_pool_free(buf->pool->pool, buf->safe, buf->safe_dma_addr);
         else
@@ -396,7 +413,6 @@ dma_addr_t
 dma_map_single(struct device *dev, void *ptr, size_t size,
                 enum dma_data_direction dir)
 {
-        unsigned long flags;
         dma_addr_t dma_addr;
 
         dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
@@ -404,12 +420,8 @@ dma_map_single(struct device *dev, void *ptr, size_t size,
 
         BUG_ON(dir == DMA_NONE);
 
-        local_irq_save(flags);
-
         dma_addr = map_single(dev, ptr, size, dir);
 
-        local_irq_restore(flags);
-
         return dma_addr;
 }
 
@@ -424,25 +436,18 @@ void
 dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
                         enum dma_data_direction dir)
 {
-        unsigned long flags;
-
         dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
                 __func__, (void *) dma_addr, size, dir);
 
         BUG_ON(dir == DMA_NONE);
 
-        local_irq_save(flags);
-
         unmap_single(dev, dma_addr, size, dir);
-
-        local_irq_restore(flags);
 }
 
 int
 dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
                 enum dma_data_direction dir)
 {
-        unsigned long flags;
         int i;
 
         dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
@@ -450,8 +455,6 @@ dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
 
         BUG_ON(dir == DMA_NONE);
 
-        local_irq_save(flags);
-
         for (i = 0; i < nents; i++, sg++) {
                 struct page *page = sg->page;
                 unsigned int offset = sg->offset;
@@ -462,8 +465,6 @@ dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
                         map_single(dev, ptr, length, dir);
         }
 
-        local_irq_restore(flags);
-
         return nents;
 }
 
@@ -471,7 +472,6 @@ void
 dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
                 enum dma_data_direction dir)
 {
-        unsigned long flags;
         int i;
 
         dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
@@ -479,55 +479,38 @@ dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
 
         BUG_ON(dir == DMA_NONE);
 
-        local_irq_save(flags);
-
         for (i = 0; i < nents; i++, sg++) {
                 dma_addr_t dma_addr = sg->dma_address;
                 unsigned int length = sg->length;
 
                 unmap_single(dev, dma_addr, length, dir);
         }
-
-        local_irq_restore(flags);
 }
 
 void
 dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr, size_t size,
                                 enum dma_data_direction dir)
 {
-        unsigned long flags;
-
         dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
                 __func__, (void *) dma_addr, size, dir);
 
-        local_irq_save(flags);
-
         sync_single(dev, dma_addr, size, dir);
-
-        local_irq_restore(flags);
 }
 
 void
 dma_sync_single_for_device(struct device *dev, dma_addr_t dma_addr, size_t size,
                                 enum dma_data_direction dir)
 {
-        unsigned long flags;
-
         dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
                 __func__, (void *) dma_addr, size, dir);
 
-        local_irq_save(flags);
-
         sync_single(dev, dma_addr, size, dir);
-
-        local_irq_restore(flags);
 }
 
 void
 dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nents,
                         enum dma_data_direction dir)
 {
-        unsigned long flags;
         int i;
 
         dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
@@ -535,23 +518,18 @@ dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nents,
 
         BUG_ON(dir == DMA_NONE);
 
-        local_irq_save(flags);
-
         for (i = 0; i < nents; i++, sg++) {
                 dma_addr_t dma_addr = sg->dma_address;
                 unsigned int length = sg->length;
 
                 sync_single(dev, dma_addr, length, dir);
         }
-
-        local_irq_restore(flags);
 }
 
 void
 dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int nents,
                         enum dma_data_direction dir)
 {
-        unsigned long flags;
         int i;
 
         dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
@@ -559,16 +537,12 @@ dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int nents,
 
         BUG_ON(dir == DMA_NONE);
 
-        local_irq_save(flags);
-
         for (i = 0; i < nents; i++, sg++) {
                 dma_addr_t dma_addr = sg->dma_address;
                 unsigned int length = sg->length;
 
                 sync_single(dev, dma_addr, length, dir);
         }
-
-        local_irq_restore(flags);
 }
 
 static int
@@ -622,6 +596,7 @@ dmabounce_register_dev(struct device *dev, unsigned long small_buffer_size,
 
         device_info->dev = dev;
         INIT_LIST_HEAD(&device_info->safe_buffers);
+        rwlock_init(&device_info->lock);
 
 #ifdef STATS
         device_info->total_allocs = 0;