[PATCH V9 09/13] MIPS: Loongson: Add swiotlb to support big memory (>4GB)

This is probably a workaround because Loongson doesn't support DMA address above 4GB. If memory is more than 4GB, CONFIG_SWIOTLB and ZONE_DMA32 should be selected. In this way, DMA pages are allocated below 4GB preferably. However, CONFIG_SWIOTLB+ZONE_DMA32 is not enough, so, we provide a

[PATCH V9 09/13] MIPS: Loongson: Add swiotlb to support big memory (4GB)

This is probably a workaround because Loongson doesn't support DMA address above 4GB. If memory is more than 4GB, CONFIG_SWIOTLB and ZONE_DMA32 should be selected. In this way, DMA pages are allocated below 4GB preferably. However, CONFIG_SWIOTLB+ZONE_DMA32 is not enough, so, we provide a