Merge tag 'dma-mapping-4.20-3' of git://git.infradead.org/users/hch/dma-mapping

Pull dma-mapping fixes from Christoph Hellwig:
 "Two dma-direct / swiotlb regressions fixes:

   - zero is a valid physical address on some arm boards, we can't use
     it as the error value

   - don't try to cache flush the error return value (no matter what it
     is)"

* tag 'dma-mapping-4.20-3' of git://git.infradead.org/users/hch/dma-mapping:
  swiotlb: Skip cache maintenance on map error
  dma-direct: Make DIRECT_MAPPING_ERROR viable for SWIOTLB

2 files changed, 3 insertions, 2 deletions

diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index bd73e7a91410..9e66bfe369aa 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -5,7 +5,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/mem_encrypt.h>
 
-#define DIRECT_MAPPING_ERROR            0
+#define DIRECT_MAPPING_ERROR            (~(dma_addr_t)0)
 
 #ifdef CONFIG_ARCH_HAS_PHYS_TO_DMA
 #include <asm/dma-direct.h>
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 5731daa09a32..045930e32c0e 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -679,7 +679,8 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
         }
 
         if (!dev_is_dma_coherent(dev) &&
-            (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
+            (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0 &&
+            dev_addr != DIRECT_MAPPING_ERROR)
                 arch_sync_dma_for_device(dev, phys, size, dir);
 
         return dev_addr;