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>

1 files changed, 40 insertions, 51 deletions

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index f6b6bfa88ecf..f61a5707823a 100644
--- 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);