[PATCH] dma: mmp_pdma: support for getting residual bytes

[Xiang Wang <wangxfdu@gmail.com>]

From: Xiang Wang <wangx@marvell.com>

In some of our drivers (e.g. UART) we may stop a running DMA
before it finishes. So we need to know how many bytes have
been transferred.

Signed-off-by: Xiang Wang <wangx@marvell.com>
---
 drivers/dma/mmp_pdma.c |   77 +++++++++++++++++++++++++++++++++++++++++++-----
 1 files changed, 69 insertions(+), 8 deletions(-)

diff --git a/drivers/dma/mmp_pdma.c b/drivers/dma/mmp_pdma.c
index 76a8dcf..0c623cc 100644
--- a/drivers/dma/mmp_pdma.c
+++ b/drivers/dma/mmp_pdma.c
@@ -104,7 +104,8 @@ struct mmp_pdma_chan {
 	spinlock_t desc_lock;		/* Descriptor list lock */
 	struct list_head chain_pending;	/* Link descriptors queue for pending */
 	struct list_head chain_running;	/* Link descriptors queue for running */
-	bool idle;			/* channel statue machine */
+	enum dma_status status; /* channel status machine */
+	u32 bytes_residue;
 
 	struct dma_pool *desc_pool;	/* Descriptors pool */
 };
@@ -270,7 +271,7 @@ static void start_pending_queue(struct mmp_pdma_chan *chan)
 	struct mmp_pdma_desc_sw *desc;
 
 	/* still in running, irq will start the pending list */
-	if (!chan->idle) {
+	if (chan->status == DMA_IN_PROGRESS) {
 		dev_dbg(chan->dev, "DMA controller still busy\n");
 		return;
 	}
@@ -307,7 +308,55 @@ static void start_pending_queue(struct mmp_pdma_chan *chan)
 	 */
 	set_desc(chan->phy, desc->async_tx.phys);
 	enable_chan(chan->phy);
-	chan->idle = false;
+	chan->status = DMA_IN_PROGRESS;
+	chan->bytes_residue = 0;
+}
+
+/*
+ * Get the number of bytes untransferred by DMA.
+ */
+static u32 mmp_pdma_get_bytes_residue(struct mmp_pdma_chan *chan)
+{
+	u32 reg, orig_pos, cur_pos, residue = 0;
+	struct mmp_pdma_desc_sw *desc_sw;
+	struct list_head *list_chain = NULL;
+
+	/*
+	 * When a phy channel is unavailable, maybe its destroied, return last
+	 * stored value for safe.
+	 */
+	if (!chan || !chan->phy)
+		return chan->bytes_residue;
+
+	if (!list_empty(&chan->chain_running))
+		list_chain = &chan->chain_running;
+	else
+		return 0;
+
+	desc_sw = list_first_entry(list_chain, struct mmp_pdma_desc_sw, node);
+
+	switch (chan->dir) {
+	case DMA_DEV_TO_MEM:
+		reg = (chan->phy->idx << 4) + DTADR;
+		cur_pos = readl_relaxed(chan->phy->base + reg);
+		orig_pos = desc_sw->desc.dtadr;
+		break;
+	case DMA_MEM_TO_DEV:
+		reg = (chan->phy->idx << 4) + DSADR;
+		cur_pos = readl_relaxed(chan->phy->base + reg);
+		orig_pos = desc_sw->desc.dsadr;
+		break;
+	case DMA_MEM_TO_MEM:
+		reg = (chan->phy->idx << 4) + DTADR;
+		cur_pos = readl_relaxed(chan->phy->base + reg);
+		orig_pos = desc_sw->desc.dtadr;
+		break;
+	default:
+		return 0;
+	}
+
+	residue = (u32)(desc_sw->desc.dcmd & DCMD_LENGTH) + orig_pos - cur_pos;
+	return residue;
 }
 
 
@@ -381,7 +430,7 @@ static int mmp_pdma_alloc_chan_resources(struct dma_chan *dchan)
 		chan->phy->vchan = NULL;
 		chan->phy = NULL;
 	}
-	chan->idle = true;
+	chan->status = DMA_SUCCESS;
 	chan->dev_addr = 0;
 	return 1;
 }
@@ -409,7 +458,7 @@ static void mmp_pdma_free_chan_resources(struct dma_chan *dchan)
 
 	dma_pool_destroy(chan->desc_pool);
 	chan->desc_pool = NULL;
-	chan->idle = true;
+	chan->status = DMA_SUCCESS;
 	chan->dev_addr = 0;
 	if (chan->phy) {
 		chan->phy->vchan = NULL;
@@ -589,7 +638,13 @@ static int mmp_pdma_control(struct dma_chan *dchan, enum dma_ctrl_cmd cmd,
 		mmp_pdma_free_desc_list(chan, &chan->chain_pending);
 		mmp_pdma_free_desc_list(chan, &chan->chain_running);
 		spin_unlock_irqrestore(&chan->desc_lock, flags);
-		chan->idle = true;
+		chan->status = DMA_SUCCESS;
+		chan->bytes_residue = 0;
+		break;
+	case DMA_PAUSE:
+		disable_chan(chan->phy);
+		chan->status = DMA_PAUSED;
+		chan->bytes_residue = mmp_pdma_get_bytes_residue(chan);
 		break;
 	case DMA_SLAVE_CONFIG:
 		if (cfg->direction == DMA_DEV_TO_MEM) {
@@ -637,7 +692,8 @@ static enum dma_status mmp_pdma_tx_status(struct dma_chan *dchan,
 	unsigned long flags;
 
 	spin_lock_irqsave(&chan->desc_lock, flags);
-	ret = dma_cookie_status(dchan, cookie, txstate);
+	ret = chan->status;
+	dma_set_residue(txstate, chan->bytes_residue);
 	spin_unlock_irqrestore(&chan->desc_lock, flags);
 
 	return ret;
@@ -684,6 +740,8 @@ static void dma_do_tasklet(unsigned long data)
 		dev_dbg(chan->dev, "completed_cookie=%d\n", cookie);
 	}
 
+	/* update bytes_residue so that the user can query later on */
+	chan->bytes_residue = mmp_pdma_get_bytes_residue(chan);
 	/*
 	 * move the descriptors to a temporary list so we can drop the lock
 	 * during the entire cleanup operation
@@ -691,7 +749,7 @@ static void dma_do_tasklet(unsigned long data)
 	list_splice_tail_init(&chan->chain_running, &chain_cleanup);
 
 	/* the hardware is now idle and ready for more */
-	chan->idle = true;
+	chan->status = DMA_SUCCESS;
 
 	/* Start any pending transactions automatically */
 	start_pending_queue(chan);
@@ -750,6 +808,9 @@ static int mmp_pdma_chan_init(struct mmp_pdma_device *pdev,
 	INIT_LIST_HEAD(&chan->chain_pending);
 	INIT_LIST_HEAD(&chan->chain_running);
 
+	chan->status = DMA_SUCCESS;
+	chan->bytes_residue = 0;
+
 	/* register virt channel to dma engine */
 	list_add_tail(&chan->chan.device_node,
 			&pdev->device.channels);
-- 
1.7.5.4