ARM: another fix for the DMA mapping checks

Peter reports that OMAP audio broke with the recent fix for these
checks, caused by OMAP audio using a 64-bit DMA mask.  We should
allow 64-bit DMA masks even with 32-bit dma_addr_t if we can be sure
the amount of RAM we have won't allow the 32-bit dma_addr_t to
overflow.  Unfortunately, the checks to detect overflow were not
correct.

Tested-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
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 f6b6bfa..f61a570 100644 (file)
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -158,13 +158,49 @@ struct dma_map_ops arm_coherent_dma_ops = {
 };
 EXPORT_SYMBOL(arm_coherent_dma_ops);
 
+static int __dma_supported(struct device *dev, u64 mask, bool warn)
+{
+       unsigned long max_dma_pfn;
+
+       /*
+        * If the mask allows for more memory than we can address,
+        * and we actually have that much memory, then we must
+        * indicate that DMA to this device is not supported.
+        */
+       if (sizeof(mask) != sizeof(dma_addr_t) &&
+           mask > (dma_addr_t)~0 &&
+           dma_to_pfn(dev, ~0) < max_pfn) {
+               if (warn) {
+                       dev_warn(dev, "Coherent DMA mask %#llx is larger than dma_addr_t allows\n",
+                                mask);
+                       dev_warn(dev, "Driver did not use or check the return value from dma_set_coherent_mask()?\n");
+               }
+               return 0;
+       }
+
+       max_dma_pfn = min(max_pfn, arm_dma_pfn_limit);
+
+       /*
+        * Translate the device's DMA mask to a PFN limit.  This
+        * PFN number includes the page which we can DMA to.
+        */
+       if (dma_to_pfn(dev, mask) < max_dma_pfn) {
+               if (warn)
+                       dev_warn(dev, "Coherent DMA mask %#llx (pfn %#lx-%#lx) covers a smaller range of system memory than the DMA zone pfn 0x0-%#lx\n",
+                                mask,
+                                dma_to_pfn(dev, 0), dma_to_pfn(dev, mask) + 1,
+                                max_dma_pfn + 1);
+               return 0;
+       }
+
+       return 1;
+}
+
 static u64 get_coherent_dma_mask(struct device *dev)
 {
        u64 mask = (u64)DMA_BIT_MASK(32);
 
        if (dev) {
-               unsigned long max_dma_pfn;
-
                mask = dev->coherent_dma_mask;
 
                /*
@@ -176,34 +212,8 @@ static u64 get_coherent_dma_mask(struct device *dev)
                        return 0;
                }
 
-               max_dma_pfn = min(max_pfn, arm_dma_pfn_limit);
-
-               /*
-                * If the mask allows for more memory than we can address,
-                * and we actually have that much memory, then fail the
-                * allocation.
-                */
-               if (sizeof(mask) != sizeof(dma_addr_t) &&
-                   mask > (dma_addr_t)~0 &&
-                   dma_to_pfn(dev, ~0) > max_dma_pfn) {
-                       dev_warn(dev, "Coherent DMA mask %#llx is larger than dma_addr_t allows\n",
-                                mask);
-                       dev_warn(dev, "Driver did not use or check the return value from dma_set_coherent_mask()?\n");
-                       return 0;
-               }
-
-               /*
-                * Now check that the mask, when translated to a PFN,
-                * fits within the allowable addresses which we can
-                * allocate.
-                */
-               if (dma_to_pfn(dev, mask) < max_dma_pfn) {
-                       dev_warn(dev, "Coherent DMA mask %#llx (pfn %#lx-%#lx) covers a smaller range of system memory than the DMA zone pfn 0x0-%#lx\n",
-                                mask,
-                                dma_to_pfn(dev, 0), dma_to_pfn(dev, mask) + 1,
-                                arm_dma_pfn_limit + 1);
+               if (!__dma_supported(dev, mask, true))
                        return 0;
-               }
        }
 
        return mask;
@@ -1032,28 +1042,7 @@ void arm_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
  */
 int dma_supported(struct device *dev, u64 mask)
 {
-       unsigned long limit;
-
-       /*
-        * If the mask allows for more memory than we can address,
-        * and we actually have that much memory, then we must
-        * indicate that DMA to this device is not supported.
-        */
-       if (sizeof(mask) != sizeof(dma_addr_t) &&
-           mask > (dma_addr_t)~0 &&
-           dma_to_pfn(dev, ~0) > arm_dma_pfn_limit)
-               return 0;
-
-       /*
-        * Translate the device's DMA mask to a PFN limit.  This
-        * PFN number includes the page which we can DMA to.
-        */
-       limit = dma_to_pfn(dev, mask);
-
-       if (limit < arm_dma_pfn_limit)
-               return 0;
-
-       return 1;
+       return __dma_supported(dev, mask, false);
 }
 EXPORT_SYMBOL(dma_supported);