ARM: 8387/1: arm/mm/dma-mapping.c: Add arm_coherent_dma_mmap

When dma-coherent transfers are enabled, the mmap call must
not change the pg_prot flags in the vma struct.

Split the arm_dma_mmap into a common and specific parts,
and add a "arm_coherent_dma_mmap" implementation that does
not alter the page protection flags.

Tested on a topic-miami board (Zynq) using the ACP port
to transfer data between FPGA and CPU using the Dyplo
framework. Without this patch, byte-wise access to mmapped
coherent DMA memory was about 20x slower because of the
memory being marked as non-cacheable, and transfer speeds
would not exceed 240MB/s.

After this patch, the mapped memory is cacheable and the
transfer speed is again 600MB/s (limited by the FPGA) when
the data is in the L2 cache, while data integrity is being
maintained.

The patch has no effect on non-coherent DMA.

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 09c5fe3..d6f5256 100644 (file)
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -148,11 +148,14 @@ static void *arm_coherent_dma_alloc(struct device *dev, size_t size,
        dma_addr_t *handle, gfp_t gfp, struct dma_attrs *attrs);
 static void arm_coherent_dma_free(struct device *dev, size_t size, void *cpu_addr,
                                  dma_addr_t handle, struct dma_attrs *attrs);
+static int arm_coherent_dma_mmap(struct device *dev, struct vm_area_struct *vma,
+                void *cpu_addr, dma_addr_t dma_addr, size_t size,
+                struct dma_attrs *attrs);
 
 struct dma_map_ops arm_coherent_dma_ops = {
        .alloc                  = arm_coherent_dma_alloc,
        .free                   = arm_coherent_dma_free,
-       .mmap                   = arm_dma_mmap,
+       .mmap                   = arm_coherent_dma_mmap,
        .get_sgtable            = arm_dma_get_sgtable,
        .map_page               = arm_coherent_dma_map_page,
        .map_sg                 = arm_dma_map_sg,
@@ -690,10 +693,7 @@ static void *arm_coherent_dma_alloc(struct device *dev, size_t size,
                           attrs, __builtin_return_address(0));
 }
 
-/*
- * Create userspace mapping for the DMA-coherent memory.
- */
-int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma,
+static int __arm_dma_mmap(struct device *dev, struct vm_area_struct *vma,
                 void *cpu_addr, dma_addr_t dma_addr, size_t size,
                 struct dma_attrs *attrs)
 {
@@ -704,8 +704,6 @@ int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma,
        unsigned long pfn = dma_to_pfn(dev, dma_addr);
        unsigned long off = vma->vm_pgoff;
 
-       vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot);
-
        if (dma_mmap_from_coherent(dev, vma, cpu_addr, size, &ret))
                return ret;
 
@@ -720,6 +718,26 @@ int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma,
        return ret;
 }
 
+/*
+ * Create userspace mapping for the DMA-coherent memory.
+ */
+static int arm_coherent_dma_mmap(struct device *dev, struct vm_area_struct *vma,
+                void *cpu_addr, dma_addr_t dma_addr, size_t size,
+                struct dma_attrs *attrs)
+{
+       return __arm_dma_mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
+}
+
+int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma,
+                void *cpu_addr, dma_addr_t dma_addr, size_t size,
+                struct dma_attrs *attrs)
+{
+#ifdef CONFIG_MMU
+       vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot);
+#endif /* CONFIG_MMU */
+       return __arm_dma_mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
+}
+
 /*
  * Free a buffer as defined by the above mapping.
  */