[v3 1/2] dma: mmp_pdma: add support for residue reporting

[zonque@gmail.com (Daniel Mack)]

In order to report the channel's residue, we have to memorize the first
dma buffer position when the channel is configured.

Signed-off-by: Daniel Mack <zonque@gmail.com>
---
 drivers/dma/mmp_pdma.c | 45 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 43 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/mmp_pdma.c b/drivers/dma/mmp_pdma.c
index 579f79a..d66340a 100644
--- a/drivers/dma/mmp_pdma.c
+++ b/drivers/dma/mmp_pdma.c
@@ -28,8 +28,8 @@
 #define DALGN		0x00a0
 #define DINT		0x00f0
 #define DDADR		0x0200
-#define DSADR		0x0204
-#define DTADR		0x0208
+#define DSADR(n)	(0x0204 + ((n) << 4))
+#define DTADR(n)	(0x0208 + ((n) << 4))
 #define DCMD		0x020c
 
 #define DCSR_RUN	(1 << 31)	/* Run Bit (read / write) */
@@ -97,6 +97,11 @@ struct mmp_pdma_chan {
 	struct dma_async_tx_descriptor desc;
 	struct mmp_pdma_phy *phy;
 	enum dma_transfer_direction dir;
+	/*
+	 * We memorize the original total length so we can later determine the
+	 * channel's residue.
+	 */
+	u32 total_len;
 
 	/* channel's basic info */
 	struct tasklet_struct tasklet;
@@ -470,6 +475,8 @@ mmp_pdma_prep_memcpy(struct dma_chan *dchan,
 		chan->dcmd |= DCMD_BURST32;
 	}
 
+	chan->total_len = len;
+
 	do {
 		/* Allocate the link descriptor from DMA pool */
 		new = mmp_pdma_alloc_descriptor(chan);
@@ -541,11 +548,14 @@ mmp_pdma_prep_slave_sg(struct dma_chan *dchan, struct scatterlist *sgl,
 		return NULL;
 
 	chan->byte_align = false;
+	chan->total_len = 0;
 
 	for_each_sg(sgl, sg, sg_len, i) {
 		addr = sg_dma_address(sg);
 		avail = sg_dma_len(sgl);
 
+		chan->total_len += avail;
+
 		do {
 			len = min_t(size_t, avail, PDMA_MAX_DESC_BYTES);
 			if (addr & 0x7)
@@ -666,6 +676,36 @@ static int mmp_pdma_control(struct dma_chan *dchan, enum dma_ctrl_cmd cmd,
 	return ret;
 }
 
+static unsigned int mmp_pdma_residue(struct mmp_pdma_chan *chan)
+{
+	struct mmp_pdma_desc_sw *sw;
+	u32 curr, done = 0;
+
+	if (chan->dir == DMA_DEV_TO_MEM)
+		curr = readl(chan->phy->base + DTADR(chan->phy->idx));
+	else
+		curr = readl(chan->phy->base + DSADR(chan->phy->idx));
+
+	list_for_each_entry(sw, &chan->chain_running, node) {
+		u32 start;
+		u32 len = sw->desc.dcmd & DCMD_LENGTH;
+
+		if (chan->dir == DMA_DEV_TO_MEM)
+			start = sw->desc.dtadr;
+		else
+			start = sw->desc.dsadr;
+
+		if (curr >= start && curr <= (start + len)) {
+			done += curr - start;
+			break;
+		}
+
+		done += len;
+	}
+
+	return chan->total_len - done;
+}
+
 static enum dma_status mmp_pdma_tx_status(struct dma_chan *dchan,
 			dma_cookie_t cookie, struct dma_tx_state *txstate)
 {
@@ -675,6 +715,7 @@ static enum dma_status mmp_pdma_tx_status(struct dma_chan *dchan,
 
 	spin_lock_irqsave(&chan->desc_lock, flags);
 	ret = dma_cookie_status(dchan, cookie, txstate);
+	txstate->residue = mmp_pdma_residue(chan);
 	spin_unlock_irqrestore(&chan->desc_lock, flags);
 
 	return ret;
-- 
1.8.3.1