dmaengine: sprd: Support DMA link-list mode

The Spreadtrum DMA can support the link-list transaction mode, which means
DMA controller can do transaction one by one automatically once we linked
these transaction by link-list register.

Signed-off-by: Eric Long <eric.long@spreadtrum.com>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/sprd-dma.c

@@ -68,6 +68,7 @@
 
 /* SPRD_DMA_CHN_CFG register definition */
 #define SPRD_DMA_CHN_EN			BIT(0)
+#define SPRD_DMA_LINKLIST_EN		BIT(4)
 #define SPRD_DMA_WAIT_BDONE_OFFSET	24
 #define SPRD_DMA_DONOT_WAIT_BDONE	1
 
@@ -103,7 +104,7 @@
 #define SPRD_DMA_REQ_MODE_MASK		GENMASK(1, 0)
 #define SPRD_DMA_FIX_SEL_OFFSET		21
 #define SPRD_DMA_FIX_EN_OFFSET		20
-#define SPRD_DMA_LLIST_END_OFFSET	19
+#define SPRD_DMA_LLIST_END		BIT(19)
 #define SPRD_DMA_FRG_LEN_MASK		GENMASK(16, 0)
 
 /* SPRD_DMA_CHN_BLK_LEN register definition */
@@ -164,6 +165,7 @@ struct sprd_dma_desc {
 struct sprd_dma_chn {
 	struct virt_dma_chan	vc;
 	void __iomem		*chn_base;
+	struct sprd_dma_linklist	linklist;
 	struct dma_slave_config	slave_cfg;
 	u32			chn_num;
 	u32			dev_id;
@@ -582,7 +584,8 @@ static int sprd_dma_get_step(enum dma_slave_buswidth buswidth)
 }
 
 static int sprd_dma_fill_desc(struct dma_chan *chan,
-			      struct sprd_dma_desc *sdesc,
+			      struct sprd_dma_chn_hw *hw,
+			      unsigned int sglen, int sg_index,
 			      dma_addr_t src, dma_addr_t dst, u32 len,
 			      enum dma_transfer_direction dir,
 			      unsigned long flags,
@@ -590,7 +593,6 @@ static int sprd_dma_fill_desc(struct dma_chan *chan,
 {
 	struct sprd_dma_dev *sdev = to_sprd_dma_dev(chan);
 	struct sprd_dma_chn *schan = to_sprd_dma_chan(chan);
-	struct sprd_dma_chn_hw *hw = &sdesc->chn_hw;
 	u32 req_mode = (flags >> SPRD_DMA_REQ_SHIFT) & SPRD_DMA_REQ_MODE_MASK;
 	u32 int_mode = flags & SPRD_DMA_INT_MASK;
 	int src_datawidth, dst_datawidth, src_step, dst_step;
@@ -670,12 +672,52 @@ static int sprd_dma_fill_desc(struct dma_chan *chan,
 	temp |= (src_step & SPRD_DMA_TRSF_STEP_MASK) << SPRD_DMA_SRC_TRSF_STEP_OFFSET;
 	hw->trsf_step = temp;
 
+	/* link-list configuration */
+	if (schan->linklist.phy_addr) {
+		if (sg_index == sglen - 1)
+			hw->frg_len |= SPRD_DMA_LLIST_END;
+
+		hw->cfg |= SPRD_DMA_LINKLIST_EN;
+
+		/* link-list index */
+		temp = (sg_index + 1) % sglen;
+		/* Next link-list configuration's physical address offset */
+		temp = temp * sizeof(*hw) + SPRD_DMA_CHN_SRC_ADDR;
+		/*
+		 * Set the link-list pointer point to next link-list
+		 * configuration's physical address.
+		 */
+		hw->llist_ptr = schan->linklist.phy_addr + temp;
+	} else {
+		hw->llist_ptr = 0;
+	}
+
 	hw->frg_step = 0;
 	hw->src_blk_step = 0;
 	hw->des_blk_step = 0;
 	return 0;
 }
 
+static int sprd_dma_fill_linklist_desc(struct dma_chan *chan,
+				       unsigned int sglen, int sg_index,
+				       dma_addr_t src, dma_addr_t dst, u32 len,
+				       enum dma_transfer_direction dir,
+				       unsigned long flags,
+				       struct dma_slave_config *slave_cfg)
+{
+	struct sprd_dma_chn *schan = to_sprd_dma_chan(chan);
+	struct sprd_dma_chn_hw *hw;
+
+	if (!schan->linklist.virt_addr)
+		return -EINVAL;
+
+	hw = (struct sprd_dma_chn_hw *)(schan->linklist.virt_addr +
+					sg_index * sizeof(*hw));
+
+	return sprd_dma_fill_desc(chan, hw, sglen, sg_index, src, dst, len,
+				  dir, flags, slave_cfg);
+}
+
 static struct dma_async_tx_descriptor *
 sprd_dma_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
 			 size_t len, unsigned long flags)
@@ -744,10 +786,20 @@ sprd_dma_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 	u32 len = 0;
 	int ret, i;
 
-	/* TODO: now we only support one sg for each DMA configuration. */
-	if (!is_slave_direction(dir) || sglen > 1)
+	if (!is_slave_direction(dir))
 		return NULL;
 
+	if (context) {
+		struct sprd_dma_linklist *ll_cfg =
+			(struct sprd_dma_linklist *)context;
+
+		schan->linklist.phy_addr = ll_cfg->phy_addr;
+		schan->linklist.virt_addr = ll_cfg->virt_addr;
+	} else {
+		schan->linklist.phy_addr = 0;
+		schan->linklist.virt_addr = 0;
+	}
+
 	sdesc = kzalloc(sizeof(*sdesc), GFP_NOWAIT);
 	if (!sdesc)
 		return NULL;
@@ -762,10 +814,25 @@ sprd_dma_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 			src = slave_cfg->src_addr;
 			dst = sg_dma_address(sg);
 		}
+
+		/*
+		 * The link-list mode needs at least 2 link-list
+		 * configurations. If there is only one sg, it doesn't
+		 * need to fill the link-list configuration.
+		 */
+		if (sglen < 2)
+			break;
+
+		ret = sprd_dma_fill_linklist_desc(chan, sglen, i, src, dst, len,
+						  dir, flags, slave_cfg);
+		if (ret) {
+			kfree(sdesc);
+			return NULL;
+		}
 	}
 
-	ret = sprd_dma_fill_desc(chan, sdesc, src, dst, len, dir, flags,
-				 slave_cfg);
+	ret = sprd_dma_fill_desc(chan, &sdesc->chn_hw, 0, 0, src, dst, len,
+				 dir, flags, slave_cfg);
 	if (ret) {
 		kfree(sdesc);
 		return NULL;

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