diff options
Diffstat (limited to 'include/linux/dma')
| -rw-r--r-- | include/linux/dma/sprd-dma.h | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/include/linux/dma/sprd-dma.h b/include/linux/dma/sprd-dma.h index b0115e340fbc..b42b80e52cc2 100644 --- a/include/linux/dma/sprd-dma.h +++ b/include/linux/dma/sprd-dma.h @@ -58,4 +58,73 @@ enum sprd_dma_int_type { SPRD_DMA_CFGERR_INT, }; +/* + * struct sprd_dma_linklist - DMA link-list address structure + * @virt_addr: link-list virtual address to configure link-list node + * @phy_addr: link-list physical address to link DMA transfer + * + * The Spreadtrum DMA controller supports the link-list mode, that means slaves + * can supply several groups configurations (each configuration represents one + * DMA transfer) saved in memory, and DMA controller will link these groups + * configurations by writing the physical address of each configuration into the + * link-list register. + * + * Just as shown below, the link-list pointer register will be pointed to the + * physical address of 'configuration 1', and the 'configuration 1' link-list + * pointer will be pointed to 'configuration 2', and so on. + * Once trigger the DMA transfer, the DMA controller will load 'configuration + * 1' to its registers automatically, after 'configuration 1' transaction is + * done, DMA controller will load 'configuration 2' automatically, until all + * DMA transactions are done. + * + * Note: The last link-list pointer should point to the physical address + * of 'configuration 1', which can avoid DMA controller loads incorrect + * configuration when the last configuration transaction is done. + * + * DMA controller linklist memory + * ====================== ----------------------- + *| | | configuration 1 |<--- + *| DMA controller | ------->| | | + *| | | | | | + *| | | | | | + *| | | | | | + *| linklist pointer reg |---- ----| linklist pointer | | + * ====================== | ----------------------- | + * | | + * | ----------------------- | + * | | configuration 2 | | + * --->| | | + * | | | + * | | | + * | | | + * ----| linklist pointer | | + * | ----------------------- | + * | | + * | ----------------------- | + * | | configuration 3 | | + * --->| | | + * | | | + * | . | | + * . | + * . | + * . | + * | . | + * | ----------------------- | + * | | configuration n | | + * --->| | | + * | | | + * | | | + * | | | + * | linklist pointer |---- + * ----------------------- + * + * To support the link-list mode, DMA slaves should allocate one segment memory + * from always-on IRAM or dma coherent memory to store these groups of DMA + * configuration, and pass the virtual and physical address to DMA controller. + */ +struct sprd_dma_linklist { + unsigned long virt_addr; + phys_addr_t phy_addr; +}; + #endif |