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-rw-r--r--include/linux/dma/sprd-dma.h69
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