[PATCH V6 20/33] csky/dma: fix up dma_mapping error

[Guo Ren]

The arch_sync_dma_for_cpu()/arch_sync_dma_for_device() implementation is
broken for some combinations that end up in a BUG() instead of performing
the necessary flushes.

The implementation of arch should follow the following rules:
         map             for_cpu         for_device      unmap
 TO_DEV  writeback       none            writeback       none
 TO_CPU  invalidate      invalidate*     invalidate      invalidate*
 BIDIR   writeback       invalidate      writeback       invalidate

Link: https://lore.kernel.org/lkml/20180518215548.GH17671@xxxxxxxxxxxxxxxxxxxxx/
Signed-off-by: Guo Ren <ren_guo@xxxxxxxxx>
---
 arch/csky/mm/dma-mapping.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/csky/mm/dma-mapping.c b/arch/csky/mm/dma-mapping.c
index 16c2087..30a2041 100644
--- a/arch/csky/mm/dma-mapping.c
+++ b/arch/csky/mm/dma-mapping.c
@@ -217,7 +217,8 @@ void arch_sync_dma_for_device(struct device *dev, phys_addr_t paddr,
 		break;
 	case DMA_FROM_DEVICE:
 	case DMA_BIDIRECTIONAL:
-		BUG();
+		dma_wbinv_range(vaddr + offset, vaddr + offset + size);
+		break;
 	default:
 		BUG();
 	}
@@ -240,7 +241,7 @@ void arch_sync_dma_for_cpu(struct device *dev, phys_addr_t paddr,
 
 	switch (dir) {
 	case DMA_TO_DEVICE:
-		BUG();
+		break;
 	case DMA_FROM_DEVICE:
 	case DMA_BIDIRECTIONAL:
 		dma_wbinv_range(vaddr + offset, vaddr + offset + size);
-- 
2.7.4