drivers: dma-coherent: Move spinlock in dma_alloc_from_coherent()

We don't need to hold the spinlock while zeroing the allocated memory.
In case we handle big buffers this is a severe issue as other CPUs might
be spinning half a second or longer.

Signed-off-by: Bastian Hecht <bhecht@de.adit-jv.com>
Signed-off-by: George G. Davis <george_davis@mentor.com>
Signed-off-by: Mark Craske <Mark_Craske@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
index 2789f7a95b93..640a7e63c453 100644
--- a/drivers/base/dma-coherent.c
+++ b/drivers/base/dma-coherent.c
@@ -165,6 +165,7 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
         int order = get_order(size);
         unsigned long flags;
         int pageno;
+        int dma_memory_map;
 
         if (!dev)
                 return 0;
@@ -187,11 +188,12 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
          */
         *dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
         *ret = mem->virt_base + (pageno << PAGE_SHIFT);
-        if (mem->flags & DMA_MEMORY_MAP)
+        dma_memory_map = (mem->flags & DMA_MEMORY_MAP);
+        spin_unlock_irqrestore(&mem->spinlock, flags);
+        if (dma_memory_map)
                 memset(*ret, 0, size);
         else
                 memset_io(*ret, 0, size);
-        spin_unlock_irqrestore(&mem->spinlock, flags);
 
         return 1;