diff options
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/dma-mapping.h | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 55c03e5fe8cb..4254fd9bdf5d 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -59,6 +59,26 @@ #define DMA_ATTR_PRIVILEGED (1UL << 9) /* + * DMA_ATTR_MMIO - Indicates memory-mapped I/O (MMIO) region for DMA mapping + * + * This attribute indicates the physical address is not normal system + * memory. It may not be used with kmap*()/phys_to_virt()/phys_to_page() + * functions, it may not be cacheable, and access using CPU load/store + * instructions may not be allowed. + * + * Usually this will be used to describe MMIO addresses, or other non-cacheable + * register addresses. When DMA mapping this sort of address we call + * the operation Peer to Peer as a one device is DMA'ing to another device. + * For PCI devices the p2pdma APIs must be used to determine if DMA_ATTR_MMIO + * is appropriate. + * + * For architectures that require cache flushing for DMA coherence + * DMA_ATTR_MMIO will not perform any cache flushing. The address + * provided must never be mapped cacheable into the CPU. + */ +#define DMA_ATTR_MMIO (1UL << 10) + +/* * A dma_addr_t can hold any valid DMA or bus address for the platform. It can * be given to a device to use as a DMA source or target. It is specific to a * given device and there may be a translation between the CPU physical address |