[PATCH v2 1/4] dmaengine: vdma: Add support for cyclic dma mode

[Kedareswara rao Appana]

This patch adds support for AXI DMA cyclic dma mode.
In cyclic mode, DMA fetches and processes the same
BDs without interruption. The DMA continues to fetch and process
until it is stopped or reset.

Signed-off-by: Kedareswara rao Appana <appanad@xxxxxxxxxx>
---
Changes for v2:
---> Removed unnecessary memset() call.

 drivers/dma/xilinx/xilinx_vdma.c | 178 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 173 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/xilinx/xilinx_vdma.c b/drivers/dma/xilinx/xilinx_vdma.c
index df91185..3edd454 100644
--- a/drivers/dma/xilinx/xilinx_vdma.c
+++ b/drivers/dma/xilinx/xilinx_vdma.c
@@ -157,6 +157,7 @@
 /* AXI DMA Specific Masks/Bit fields */
 #define XILINX_DMA_MAX_TRANS_LEN	GENMASK(22, 0)
 #define XILINX_DMA_CR_COALESCE_MAX	GENMASK(23, 16)
+#define XILINX_DMA_CR_CYCLIC_BD_EN_MASK	BIT(4)
 #define XILINX_DMA_CR_COALESCE_SHIFT	16
 #define XILINX_DMA_BD_SOP		BIT(27)
 #define XILINX_DMA_BD_EOP		BIT(26)
@@ -278,11 +279,13 @@ struct xilinx_cdma_tx_segment {
  * @async_tx: Async transaction descriptor
  * @segments: TX segments list
  * @node: Node in the channel descriptors list
+ * @cyclic: Check for cyclic transfers.
  */
 struct xilinx_dma_tx_descriptor {
 	struct dma_async_tx_descriptor async_tx;
 	struct list_head segments;
 	struct list_head node;
+	bool cyclic;
 };
 
 /**
@@ -302,6 +305,7 @@ struct xilinx_dma_tx_descriptor {
  * @direction: Transfer direction
  * @num_frms: Number of frames
  * @has_sg: Support scatter transfers
+ * @cyclic: Check for cyclic transfers.
  * @genlock: Support genlock mode
  * @err: Channel has errors
  * @tasklet: Cleanup work after irq
@@ -312,6 +316,7 @@ struct xilinx_dma_tx_descriptor {
  * @desc_submitcount: Descriptor h/w submitted count
  * @residue: Residue for AXI DMA
  * @seg_v: Statically allocated segments base
+ * @cyclic_seg_v: Statically allocated segment base for cyclic transfers
  * @start_transfer: Differentiate b/w DMA IP's transfer
  */
 struct xilinx_dma_chan {
@@ -330,6 +335,7 @@ struct xilinx_dma_chan {
 	enum dma_transfer_direction direction;
 	int num_frms;
 	bool has_sg;
+	bool cyclic;
 	bool genlock;
 	bool err;
 	struct tasklet_struct tasklet;
@@ -340,6 +346,7 @@ struct xilinx_dma_chan {
 	u32 desc_submitcount;
 	u32 residue;
 	struct xilinx_axidma_tx_segment *seg_v;
+	struct xilinx_axidma_tx_segment *cyclic_seg_v;
 	void (*start_transfer)(struct xilinx_dma_chan *chan);
 };
 
@@ -660,13 +667,37 @@ static void xilinx_dma_free_chan_resources(struct dma_chan *dchan)
 	dev_dbg(chan->dev, "Free all channel resources.\n");
 
 	xilinx_dma_free_descriptors(chan);
-	if (chan->xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA)
+	if (chan->xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA) {
+		xilinx_dma_free_tx_segment(chan, chan->cyclic_seg_v);
 		xilinx_dma_free_tx_segment(chan, chan->seg_v);
+	}
 	dma_pool_destroy(chan->desc_pool);
 	chan->desc_pool = NULL;
 }
 
 /**
+ * xilinx_dma_chan_handle_cyclic - Cyclic dma callback
+ * @chan: Driver specific dma channel
+ * @desc: dma transaction descriptor
+ * @flags: flags for spin lock
+ */
+static void xilinx_dma_chan_handle_cyclic(struct xilinx_dma_chan *chan,
+					  struct xilinx_dma_tx_descriptor *desc,
+					  unsigned long *flags)
+{
+	dma_async_tx_callback callback;
+	void *callback_param;
+
+	callback = desc->async_tx.callback;
+	callback_param = desc->async_tx.callback_param;
+	if (callback) {
+		spin_unlock_irqrestore(&chan->lock, *flags);
+		callback(callback_param);
+		spin_lock_irqsave(&chan->lock, *flags);
+	}
+}
+
+/**
  * xilinx_dma_chan_desc_cleanup - Clean channel descriptors
  * @chan: Driver specific DMA channel
  */
@@ -681,6 +712,11 @@ static void xilinx_dma_chan_desc_cleanup(struct xilinx_dma_chan *chan)
 		dma_async_tx_callback callback;
 		void *callback_param;
 
+		if (desc->cyclic) {
+			xilinx_dma_chan_handle_cyclic(chan, desc, &flags);
+			break;
+		}
+
 		/* Remove from the list of running transactions */
 		list_del(&desc->node);
 
@@ -757,7 +793,7 @@ static int xilinx_dma_alloc_chan_resources(struct dma_chan *dchan)
 		return -ENOMEM;
 	}
 
-	if (chan->xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA)
+	if (chan->xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA) {
 		/*
 		 * For AXI DMA case after submitting a pending_list, keep
 		 * an extra segment allocated so that the "next descriptor"
@@ -768,6 +804,15 @@ static int xilinx_dma_alloc_chan_resources(struct dma_chan *dchan)
 		 */
 		chan->seg_v = xilinx_axidma_alloc_tx_segment(chan);
 
+		/*
+		 * For cyclic DMA mode we need to program the tail Descriptor
+		 * register with a value which is not a part of the BD chain
+		 * so allocating a desc segment during channel allocation for
+		 * programming tail descriptor.
+		 */
+		chan->cyclic_seg_v = xilinx_axidma_alloc_tx_segment(chan);
+	}
+
 	dma_cookie_init(dchan);
 
 	if (chan->xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA) {
@@ -1157,8 +1202,12 @@ static void xilinx_dma_start_transfer(struct xilinx_dma_chan *chan)
 
 	/* Start the transfer */
 	if (chan->has_sg) {
-		dma_ctrl_write(chan, XILINX_DMA_REG_TAILDESC,
-			       tail_segment->phys);
+		if (chan->cyclic)
+			dma_ctrl_write(chan, XILINX_DMA_REG_TAILDESC,
+				       chan->cyclic_seg_v->phys);
+		else
+			dma_ctrl_write(chan, XILINX_DMA_REG_TAILDESC,
+				       tail_segment->phys);
 	} else {
 		struct xilinx_axidma_tx_segment *segment;
 		struct xilinx_axidma_desc_hw *hw;
@@ -1209,7 +1258,8 @@ static void xilinx_dma_complete_descriptor(struct xilinx_dma_chan *chan)
 
 	list_for_each_entry_safe(desc, next, &chan->active_list, node) {
 		list_del(&desc->node);
-		dma_cookie_complete(&desc->async_tx);
+		if (!desc->cyclic)
+			dma_cookie_complete(&desc->async_tx);
 		list_add_tail(&desc->node, &chan->done_list);
 	}
 }
@@ -1397,6 +1447,11 @@ static dma_cookie_t xilinx_dma_tx_submit(struct dma_async_tx_descriptor *tx)
 	unsigned long flags;
 	int err;
 
+	if (chan->cyclic) {
+		xilinx_dma_free_tx_descriptor(chan, desc);
+		return -EBUSY;
+	}
+
 	if (chan->err) {
 		/*
 		 * If reset fails, need to hard reset the system.
@@ -1414,6 +1469,9 @@ static dma_cookie_t xilinx_dma_tx_submit(struct dma_async_tx_descriptor *tx)
 	/* Put this transaction onto the tail of the pending queue */
 	append_desc_queue(chan, desc);
 
+	if (desc->cyclic)
+		chan->cyclic = true;
+
 	spin_unlock_irqrestore(&chan->lock, flags);
 
 	return cookie;
@@ -1669,12 +1727,112 @@ error:
 }
 
 /**
+ * xilinx_dma_prep_dma_cyclic - prepare descriptors for a DMA_SLAVE transaction
+ * @chan: DMA channel
+ * @sgl: scatterlist to transfer to/from
+ * @sg_len: number of entries in @scatterlist
+ * @direction: DMA direction
+ * @flags: transfer ack flags
+ */
+static struct dma_async_tx_descriptor *xilinx_dma_prep_dma_cyclic(
+	struct dma_chan *dchan, dma_addr_t buf_addr, size_t buf_len,
+	size_t period_len, enum dma_transfer_direction direction,
+	unsigned long flags)
+{
+	struct xilinx_dma_chan *chan = to_xilinx_chan(dchan);
+	struct xilinx_dma_tx_descriptor *desc;
+	struct xilinx_axidma_tx_segment *segment, *head_segment, *prev = NULL;
+	size_t copy, sg_used;
+	unsigned int num_periods;
+	int i;
+	u32 reg;
+
+	num_periods = buf_len / period_len;
+
+	if (!is_slave_direction(direction))
+		return NULL;
+
+	/* Allocate a transaction descriptor. */
+	desc = xilinx_dma_alloc_tx_descriptor(chan);
+	if (!desc)
+		return NULL;
+
+	chan->direction = direction;
+	dma_async_tx_descriptor_init(&desc->async_tx, &chan->common);
+	desc->async_tx.tx_submit = xilinx_dma_tx_submit;
+
+	for (i = 0; i < num_periods; ++i) {
+		sg_used = 0;
+
+		while (sg_used < period_len) {
+			struct xilinx_axidma_desc_hw *hw;
+
+			/* Get a free segment */
+			segment = xilinx_axidma_alloc_tx_segment(chan);
+			if (!segment)
+				goto error;
+
+			/*
+			 * Calculate the maximum number of bytes to transfer,
+			 * making sure it is less than the hw limit
+			 */
+			copy = min_t(size_t, period_len - sg_used,
+				     XILINX_DMA_MAX_TRANS_LEN);
+			hw = &segment->hw;
+			hw->buf_addr = buf_addr + sg_used + (period_len * i);
+			hw->control = copy;
+
+			if (prev)
+				prev->hw.next_desc = segment->phys;
+
+			prev = segment;
+			sg_used += copy;
+
+			/*
+			 * Insert the segment into the descriptor segments
+			 * list.
+			 */
+			list_add_tail(&segment->node, &desc->segments);
+		}
+	}
+
+	head_segment = list_first_entry(&desc->segments,
+				   struct xilinx_axidma_tx_segment, node);
+	desc->async_tx.phys = head_segment->phys;
+
+	desc->cyclic = true;
+	reg = dma_ctrl_read(chan, XILINX_DMA_REG_DMACR);
+	reg |= XILINX_DMA_CR_CYCLIC_BD_EN_MASK;
+	dma_ctrl_write(chan, XILINX_DMA_REG_DMACR, reg);
+
+	/* For the last DMA_MEM_TO_DEV transfer, set EOP */
+	if (direction == DMA_MEM_TO_DEV) {
+		segment->hw.control |= XILINX_DMA_BD_SOP;
+		segment = list_last_entry(&desc->segments,
+					  struct xilinx_axidma_tx_segment,
+					  node);
+		segment->hw.control |= XILINX_DMA_BD_EOP;
+		segment->hw.next_desc = (u32) head_segment->phys;
+	}
+
+	return &desc->async_tx;
+
+error:
+	xilinx_dma_free_tx_descriptor(chan, desc);
+	return NULL;
+}
+
+/**
  * xilinx_dma_terminate_all - Halt the channel and free descriptors
  * @chan: Driver specific DMA Channel pointer
  */
 static int xilinx_dma_terminate_all(struct dma_chan *dchan)
 {
 	struct xilinx_dma_chan *chan = to_xilinx_chan(dchan);
+	u32 reg;
+
+	if (chan->cyclic)
+		xilinx_dma_chan_reset(chan);
 
 	/* Halt the DMA engine */
 	xilinx_dma_halt(chan);
@@ -1682,6 +1840,13 @@ static int xilinx_dma_terminate_all(struct dma_chan *dchan)
 	/* Remove and free all of the descriptors in the lists */
 	xilinx_dma_free_descriptors(chan);
 
+	if (chan->cyclic) {
+		reg = dma_ctrl_read(chan, XILINX_DMA_REG_DMACR);
+		reg &= ~XILINX_DMA_CR_CYCLIC_BD_EN_MASK;
+		dma_ctrl_write(chan, XILINX_DMA_REG_DMACR, reg);
+		chan->cyclic = false;
+	}
+
 	return 0;
 }
 
@@ -2218,7 +2383,10 @@ static int xilinx_dma_probe(struct platform_device *pdev)
 	xdev->common.device_tx_status = xilinx_dma_tx_status;
 	xdev->common.device_issue_pending = xilinx_dma_issue_pending;
 	if (xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA) {
+		dma_cap_set(DMA_CYCLIC, xdev->common.cap_mask);
 		xdev->common.device_prep_slave_sg = xilinx_dma_prep_slave_sg;
+		xdev->common.device_prep_dma_cyclic =
+					  xilinx_dma_prep_dma_cyclic;
 		/* Residue calculation is supported by only AXI DMA */
 		xdev->common.residue_granularity =
 					  DMA_RESIDUE_GRANULARITY_SEGMENT;
-- 
2.1.2